Abstract: According to the total amount of plastic film consumption and grain yields and total sown area of wheat, corn and rice from 1999 to 2001 in each county of China, the regional differences in film-mulching rate and potential of grain yield increase by plastic films application were computed and analyzed. Results of the study were concluded as follows: First, the film-mulching rate in most of the counties varied from 1% to 10%; The potential of grain yield increase per sowing area in most counties varied from 500 kg/hm² to 1500 kg/hm². Second, the spatial difference of the film-mulching rate and potential of grain yield increase is distinct, the counties with the relatively low film-mulching rate and relatively high potential of grain yield increase centre in Eastern and Central Regions of China mainly. It is concluded that more plastic films should be used in the Eastern and Central Regions to improve China grain productivity. Finally, under the rational hypothesis of the increase of film-mulching rate, the potential of grain yield increase of the whole country was estimated.