In order to study the effects of long-term straw return on the distribution and stability of aggregates and phosphorus distribution in different soil layers of wheat field in the eastern part of the Tibetan Plateau，six treatments were set up in a positioning experiment for long-term straw return，including nitrogen-phosphorus fertilizer(NP)，nitrogen-phosphorus-potassium(NPK)fertilizer，nitrogen-phosphorus fertilizer plus half amount of straw returned to the field(NPS1)，nitrogen-phosphorus fertilizer plus full amount of straw returned to the field(NPS2)，nitrogen-phosphorus-potassium fertilizer plus half amount of straw returned to the field(NPKS1)，nitrogen-phosphorus-potassium fertilizer plus full amount of straw returned to the field(NPKS2). After wheat harvest，soil samples were taken from 0–10，10–20 and 20–30 cm soil layers，and a combination of wet and dry sieving was used to determine the composition of water-stable aggregates in each soil layer，and to quantify the contents of total phosphorus，available phosphorus，and the contribution rate of available phosphorus in each aggregate component. The results showed that compared with the single application of chemical fertilizer treatments(NP and NPK)，the straw-returned treatments(NPS1，NPS2，NPKS1，NPKS2)significantly increased the content of available phosphorus in the soil layers of 0 –10 and 10 –20 cm (P < 0.05)，which was increased by 9.1%–27.4% and 5.1%–38.4%，respectively，and the content of available phosphorus of the treatment of the full amount of straw returned to field was the highest. Therefore，all straw treatments showed that the mass percentage of >2 mm aggregate decreased significantly with the increase of soil depth，and the mass percentage of <0.25 mm aggregate increased significantly with the increase of soil depth. The straw returned treatments also increased the mean weight diameter and geometric mean diameter of the aggregate，decreased the index of unstable aggregate，and enhanced the stability of the aggregate，especially the aggregate of the full amount of straw returned to the field. The straw returned treatments also significantly increased (P < 0.05)the content of available phosphorus in all soil layers and particle sizes of aggregate，with increases of 0.2%–47.2%，1.5%–63.2% and 4.0%–91.1%，respectively，in the three soil layers，and >0.25 mm aggregate were the main carriers of the contribution of available phosphorus. The full amount of straw returned to the field was more conducive to promoting the formation of large aggregate，improving the stability of the aggregate，regulating the distribution of phosphorus in the aggregate，and improving the phosphorus activity.