Oasis transformation has caused microplastic pollution in the soil while improving land productivity in arid areas. To understand its impact on the soil ecosystem, we selected four representative cotton fields with varying cultivation durations to study the characteristics of occurrence of microplastics in the topsoil and the changes in the microbial community structure and ecological function of the plastisphere. The results revealed that the abundance of microplastics in the cotton field soil in this area was positively correlated with the number of years of cultivation, and fibers and fragments of polyethylene plastics smaller than 1 mm were the main microplastic types. The yield reached 6046.67 +/- 1366.07 items/kg in the cotton field under continuous cultivation for 36 years. Oasis activity causes the plastisphere microbial community to be more strongly affected by inputs from the soil environment and crop root microorganisms, reducing its heterogeneity with soil microorganisms. The pathological fungal community in the plastisphere increased significantly with increasing cultivation duration (P < 0.05), and the plastisphere might constitute a new accumulation pool of crop pathogens in oasis cotton fields. This risk may increase with the gradual accumulation of microplastics in the soil. Our research results are helpful for further understanding the impact of microplastic inputs on the soil ecosystem in arid areas during oasis transformation and provide a reference for ensuring the agricultural safety of oases.