Based on a 7-year spring maize field experiment on the Loess Plateau, in which two treatments of urea mixed controlled release fertilizer under film mulching (the control, CU) and CU+ straw return (CS) were established to investigate the effects of long-term film mulching with straw return on nitrogen (N) pools and N saturation deficits of topsoil (0-20 cm) and subsoil (20-40 and 40-60 cm). The results showed that compared with the control, CS decreased bulk density of topsoil, increased total nitrogen content and total nitrogen storage in each soil layer, significantly increased topsoil N pool management indexes in 2019 and 2020, and significantly increased topsoil nitrate N by 173% and 176% in 2019 and 2020, respectively, but decreased topsoil ammonium N, Compared with the control, CS increased the contents of water soluble organic N, hot water extracted organic N and particulate organic N to varying degrees and slightly increased mineral-associated organic N content in topsoil, and significantly increased current N pool in fine particles and significantly decreased N saturated deficit in topsoil in both years. In conclusion, film mulching with straw return is a sustainable management measure for improving soil quality and enhancing soil N pools in dryland agricultural areas.