Taking long-term farmland positioning experiment in loessal soil of the national soil quality observation and test station in Anding district of Gansu province as the research object，the effects of long-term fertilization and plastic-mulching on yield and water use efficiency of potato and soil organic carbon in semi-arid area were studied.The results showed that plastic-mulching significantly improved the yield and water use efficiency of potato in years of insufficient and normal precipitation，and the effect was not obvious in years of relatively sufficient precipitation.Fertilization significantly affected the yield and water use efficiency of potato，and the effect of combined application of organic fertilizer and chemical fertilizer(NPKM)was the best.In the first two years of the experiment，the effect of applying chemical fertilizer(NPK)was better than that of organic fertilizer(OM)，and there was no difference in the third year of the long-term positioning experiment，but the effect of OM was better than that of NPK after the fourth year of the long-term positioning experiment.Compared with NPK treatment，the content of organic carbon of long-term organic fertilizer treatments(NPKM and OM)increased significantly by 77.35% and 69.65%，respectively，and organic carbon storage increased significantly by 70.68%～76.55% and 62.09%～63.31%，respectively，in 0～20 cm soil layer.The effects of different fertilization treatments on soil microbial biomass carbon were as follows:NPKM>OM>NPK>CK.There was significant difference between treatments，and soil microbial biomass carbon of NPKM and OM treatments increased significantly by 43.99% and 31.82%，respectively，compared with NPK，and the effect of organic fertilizer application was better than that of chemical fertilizer.Long-term plastic-mulching and NPK treatment significantly improved the content of microbial biomass carbon，however，they was no obvious effect on the content and storage of organic carbon.In conclusion，long-term organic fertilizer combined with chemical fertilizer(NPKM)or organic fertilizer(OM)can significantly improve the contents of total organic carbon and microbial biomass carbon of loessal soil in dryland，and increase organic carbon storage and promote the sequestration of farmland soil carbon，and improve yield and water use efficiency of potato.The effects of plastic-mulching on yield and water use efficiency of potato are closely related to interannual precipitation in dryland.