High crop yield and high quality are the primarily targets in intensive crop production. Although the plastic film mulch (PFM) approach has been well established for high-yielding wheat production in dryland, effects of PFM on wheat grain quality is still poorly understood. Therefore, multi-site and fixed location field experiments were conducted to investigate effects of PFM on grain yield, protein content and its components content of dryland winter wheat in 2014-2016 in the Loess Plateau of China. Compared with no mulch (NM), PFM increased the grain yield, structural protein contents and the ratio of gliadin/glutenin by 634 kg ha(-1), 11.3%-30.8% and 15.1%, respectively, but reduced the total protein and its gluten contents by 7.8% and 3.4%-15.1%. Furthermore, PFM significantly increased the proportion of albumin, globulin and gliadin to total protein by 22.3%, 44.2% and 5.5%, respectively, but decreased the proportion of glutenin by 7.4%, compared to NM. The highest grain yield, albumin and glutenin content were attained when the critical N rates were 146 kg N ha(-1), 167 kg N ha(-1) and 100 kg N ha(-1), respectively. Moreover, for every 100 kg ha(-1) increase in N fertilizer, the globulin content increased by 0.11%, but the ratio of gliadin/glutenin decreased by 0.12%. In summary, PFM did not show any benefit for gluten, while precise N fertilizer management provided an opportunity for improving grain processing quality of dryland wheat. In order to tradeoff between grain yield and its processing quality, the optimal N application rate (146-167 kg N ha(-1)) should be considered under PFM. These findings suggest that optimal N management serves as a basis for further investigation and regulation of grain protein components of wheat under PFM in the semiarid area of China and similar cropping system around the world.