The heat efficiency of one film in dry farming fields of wheat and corn is studied. It suggests that with the application of this plastic film,the soiltemperature could increase about 2-6℃ thus provided a favorable condition to the growth of winter-wheat .with a heat efficiency of 0. 997.Compared with that of single croping the heat efficiency has been raised by 24%-40%. And therefore one crop a year became two crOP a year. Per mu yield is about 440-610kg and compared with that of single croping it increased by 20%-80%.