Abstract: The dropping effect of soil temperature by film-covering on fields is studied in this paper．The resuhs show that the crop’S growing and flourishing stage(from blooming to boll opening of cotton，from tassel appearance to milky of maize，and from flowering to podding of soybean)is in the summer．Because under the film ，the crop’S branches and leaves are so flourishing and thick they can absorb more sun light，but the mid-down part of the crop has less light intensity than the coun terpart with no film-covering ． Meanwhile the temperature of the soil surface with film-covering is lower than the surface with no film -covering．In this circumstance the degree of dropping tempe rature in the cotton，maize and soybean field is 3．1℃ ．2．7℃ and 2．5℃ ．The dropping soil temperature effect with film-covering can reduce the damage of I1igh temperature to crop validly in the summer．Therefore it can increase the production．