Xinjiang was rich in organic fertilizer resources. This research aimed to explore the effects of organic replacement of phosphate fertilizer and exogenous fertilizer input of straw returning to field on soil chemical changes，cotton yield and its composition，so as to provide a reference for in-depth understanding of current cotton field fertility and determine the technical service focus of reducing phosphorus and increasing efficiency of cotton production. In this study，seven fertilization treatments were set up under the condition of membrane drip irrigation through the 5-year field micro-area positioning experiment of national gray desert soil fertility and fertilizer benefit monitoring station. Seven treatments were set up，including T1:no fertilization，T2:no phosphorus application，T3:100% fertilizer phosphorus application，T4:organic fertilizer phosphorus replacement 25% fertilizer phosphorus，T5:organic fertilizer phosphorus replacement 50% fertilizer phosphorus，and T6:fertilizer phosphorus 100%+25% organic fertilizer phosphorus，T7:fertilizer phosphorus 100%+ straw return to the field. Soil samples were collected in 2022 to investigate the effects of organic replacement of phosphorus fertilizer with different proportions and straw returning on soil chemical properties，phosphorus availability characteristics，cotton yield and its composition. The results showed that:(1)Under the condition that the amount of exogenous fertilizer nitrogen and phosphorus input(organic fertilizer and chemical fertilizer)was equal，the organic replacement of phosphate fertilizer and the return of straw to field could accelerate the transformation of soil nutrients and increase the content of soil available nutrients and total nutrients. The increases of available nitrogen，available phosphorus and available potassium content ranged from 3.0% to 25.3%，29.2% to 120.1% and 70.1% to 99.1%，respectively. Compared with the T6，T5 and T5 treatments with the highest increment after the application of exogenous fertilizer，the contents of each available nutrient were annually increased by 3.12，1.69 and 30.75 mg·kg-1 on average，respectively. Total nitrogen，total phosphorus and total potassium content increased by 21.1%-43.9%，1.59%-41.3% and 9.3%-33.6%，respectively. Compared with the T6，T6 and T5 treatments with the highest increment after the application of exogenous fertilizer，the contents of each total nutrient average annual increase rate were 0.04，0.05 and 1.36 g·kg-1，respectively. On the whole，the effect of organic replacement，increased application of organic fertilizer and straw returning to field was better than that of single chemical fertilizer，and the effect of long-term application of organic fertilizer was better than that of straw returning to field.(2)Organic matter content in the topsoil increased with the increase of organic fertilizer replacement amount. The maximum organic matter content of 50% organic replacement was 12.21 g·kg-1，with an average annual increase of 0.4 g·kg-1. The minimum increment of T1 and T2 increased by 1.04-3.44 g·kg-1，compared with the maximum increment of T1-T5. The increase rate was 11.86%-39.22%，and the overall performance was positive. Relatively high soil pH and salt content were the main factors limiting the efficient production of cotton. The return of organic fertilizer and straw to the field could reduce soil pH and salt content as a whole. The maximum decrease of pH was T1 with T5 and salt content was T5 with T3，which decreased by 3.07% and 24.48%，respectively，showing a negative effect. Combined application of organic fertilizer and straw returning enhanced the nitrogen supply capacity and phosphorus activation capacity of soil，and soil phosphoras activation coefficient increased from 1.52% to 2.78%. Due to the limitation of calcareous soil and climatic conditions in Xinjiang，the C/N，C/P and N/P showed that the grey desert soil was in a state of lack of organic matter.(3)Organic replacement of phosphate fertilizer and straw returning could maintain or promote the increase of cotton yield. Under the experimental planting pattern with a density of 240000 plants·hm-2，the seed and cotton yield of conventional fertilization，25% organic replacement，50% organic replacement，increased application of organic fertilizer and straw returning to field reached 4173.13，4196.72，4805.10，5035.51 and 4830.98 kg·hm-2，respectively，for 5 consecutive years. Comprehensive analysis of soil nutrient index，fertilizer input and cotton yield，50% organic substitution had the best effect on cotton yield under the premise of saving the amount of phosphate fertilizer，and significantly increased the yield by 20.49%，18.62% and 15.14%，compared with T1，T2 and T3，respectively. Therefore，the present study concluded that the application of 50% organic substitution technology，namely the application of phosphate(P2O5)60 kg·hm-2 and combination application of sheep manure 9784 kg·hm-2，is more feasible.