Abstract: Abstract: Plastic film mulching technique has been used widely in China because of its notable benefits such as raising soil temperature, inhibiting weed growth, promoting crop maturity and increasing production, especially in the field of cotton cultivation, almost all of them used plastic film mulching technique in XinJiang. Recycled waste plastic film and cotton straw, stubble and other trash were difficult to separate, this problem caused difficulty in reutilization of waste plastic film. A large number of recycled waste plastic films were buried or burned randomly in field which lead to secondary environment pollution. In order to separate the waste plastic film from cotton straw, stubble and other trash, realize recycling of waste plastic film and solve the problem of environment pollution results from waste plastic film at source. The movement state and trajectory of cotton straw, stubble and plastic film were simulated through building of wind field device, and suspension velocity of cotton straw, stubble and plastic film were measured in wind field. The mathematical model of separation conditions was established through analysis of stress condition of different materials in wind field and law of settling of different materials in air medium. High speed dynamic camera was used to observe the movement of the material in the wind field, the feasibility of the principle was verified. Based on results of researches above, a type of roller sieve waste plastic film and trash winnowing machine was designed. In this paper, the overall structure and working principle of the machine were introduced, the structure and size parameters of the key components of rotating sieve cylinder and the helix in rotating sieve cylinder were determined. In order to determine the relationship between the best separation effect with rotating sieve cylinder speed, the outlet velocity of wind pipe, and the material feed quantity, an orthogonal test with rotating sieve cylinder speed, the outlet velocity of wind pipe, and the material feed quantity as the experimental factors were carried out, the raw material composition after mechanical harvesting was analyzed as test condition. Primary and secondary order of plastic film rate in trash and rate of trash in plastic film were confirmed through analysis of test results. Reasons of change were analyzed, and significance tests were done for factors of plastic film rate in trash and rate of trash in plastic film. Finally, the optimal parameter combination was determined. The results proved that when the rotating sieve cylinder speed was 30 r/min, the outlet velocity of wind pipe was 15 m/s, and the material feed quantity was 250 kg/h, the operation effect was best, the rate of trash in plastic film was the least, the plastic film rate in trash was minimum, the waste plastic film production was maximum. The machine was adjusted to the best working parameters for conducting production test and verifying the foregoing conclusion. The results showed that all indexes were met the design requirements, the rate of trash in plastic film was 13.71%, the plastic film rate in trash was 0.133%, the production of waste plastic film upped to 35.8 kg/h after separating. In summary, we designed roller sieve waste plastic film and trash winnowing machine, it can realized separation of waste plastic film from cotton straw, stubble and other trash effectively. This research fills gaps in this area in China. The secondary pollution causes by waste plastic film recycling can be reduced if the machined used, the utilization rate of waste plastic film can be improved greatly.