Abstract: [Objective] To make clear plastic film mulching cotton safety period and study the effects of different degradation films on soil temperature,moisture and the yield of cotton under drip irrigation.[Method]The experiment set up 5 treatments with 3 repeated times,T1-T4 treatment was for the degradation of plastic film processing,and T5 was for ordinary plastic film processing.[Result]The results showed that: the laying of eighty-fifth days(July 17th)T1 treatment,plastic film was completely degraded and only partially degraded by T2 treatment.However,degradation began after 130 days(August 31)later by T3 treatment.T4 treatment made no degradation at all.The soil temperature was increased in April,May and June between 55.4;-62.6;,14.3;-23.5;and 9.6;-14.2;,by all treatments,in July it did show warming effect;and water retention performance of the membrane was not associated with its thickness and degradation rate,among them,T4 treatment produed the best water retention.Plastic film was laid 85 days ago,the plastic film degradation time was inversely proportional to cotton growing development and yield.And 85 days later,the film was not degraded by T3,T4 and T5 treatment,which showed no significant difference in cotton yield.[Conclusion]In summary,the plastic degradation time 85 days after the cotton flowering period can effectively exert the soil warming effect to achieve the stable production.