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Concerning the increasing of plant density is one of important ways to achieve high yield, field experiments were conducted to investigate the effects of increasing plant density and plastic film mulching on the growth and yield of spring maize, and crop evapotranspiration. The results showed that film mulching accelerated growth and development of maize. It also increased height and leaf area index of the plant at early growth stage of maize. At the late growth stage of maize, plant height of maize without film mulching was decreased with the increase of density, but no significant difference was found for plastic film mulching. Whether mulching or un-mulching, leaf area index of maize was increased with the increase of the density. Evapotranspiration increased with the increase of the density, however, film mulching reduced consumption of water and alleviated the contradiction between increase of water consumption because of the increased plant density and plant height and insufficient precipitation. Film mulching significantly increased maize yield and water use efficiency by 52.79% and 60.55% compared with un-mulching. The grain yield and the water use efficiency of un-mulching and film mulching treatments were all increased with the increase of the plant density until a plateau and then declined. The difference was that the maximum yield of un-mulching was 8466.02kg/hm2 and it was achieved at 52500 plants/hm2, however, the maximum yield of film mulching was 12778.47kg/hm2 and it was achieved at 82500 plants/hm2. As a result, the optimum planting densities on eastern Loess Plateau for film mulching and un-mulching of spring maize were 52500 plants/hm2 and 82500 plants/hm2.