In order to explore the regulation effects of straw return replacing the application of potassium fertilizer on dryland summer maize—winter wheat rotation system, four treatments including no fertilizer (CK), nitrogen and phosphorus fertilizer (NP), nitrogen, phosphorus and potassium fertilizer (NPK), nitrogen and phosphorus fertilizer plus straw returning (NPS) were selected based on the long-term located field experiment which started in 2007 at dry farming platform (Luoyang) of Chinese Academy of Agricultural Sciences. We investigated the grain yield, water and fertilizer use efficiency of summer maize and winter wheat rotation system from 2015 to 2020, as well as the content of organic matter, total nitrogen, available phosphorus and available potassium in 0—60 cm soil layer, and soil nitrate accumulation in 0—260 cm soil layer at harvest of winter wheat in 2020. Compared with NP, NPK significantly increased the content of available potassium in the 0—60 cm soil layer, but did not change the grain yield, water and fertilizer use efficiency of summer maize and winter wheat rotation system, while NPS was beneficial to improve soil nutrient, and significantly increased the grain yield, water and fertilizer use efficiency in summer maize and whole year. Compared with NPK, NPS significantly increased the organic matter content by 10.68% in 0—20 cm soil layer, the grain yield, water use efficiency, and the agronomic efficiency of N(P) fertilizer in summer maize and whole year increased by 20.91%, 33.77%, 114.39% and 13.60%, 13.63%, 65.41%, respectively, but significantly decreased the available phosphorus content by 7.43% in 0—20 cm soil layer and the available potassium content by 14.31% in 0—60 cm soil layer. Compared with NP and NPK, the nitrate accumulation in NPS was increased by 37.14% and 25.92% in 0—100 cm soil layer, and decreased by 32.33% and 21.64% in 160—260 cm soil layer. In conclusion, straw return could be used for replacing the application of potassium fertilizer on the basis of N and P fertilizer, because it could not only increase the content of organic matter and total nitrogen in 0—20 cm soil layer and nitrate accumulation in 0—100 cm soil layer, thereby improving the grain yield, water and fertilizer use efficiency in summer maize and whole year, but also reduced the risk of soil nitrate leaching to deep layer. Therefore, NPS was a suitable measure in dryland summer maize—winter wheat rotation system, but it should be paid more attention to the problems of the decrease of available phosphorus and available potassium in soil.