Abstract: To study the effects and interactions of different straw return modes and planting densities on maize leaf-soil ecological stoichiometric characteristics at different fertility periods, and providetheoretical basis for the application and promotion of the stover return to the field technologyfor the effective utilization in the Ningxia Yellow River Irrigation Area of soil carbon, nitrogen and phosphorus resources for nutrients. Using a two-factor spilt-plot experimental design, the main plot consists of two straw returning modes: H0 (no straw return) and H1 (complete straw crushing and deep plowing return); the subplot are three planting densities, in the following order: D1 (67 500 plants·hm⁻²), D2 (82 500 plants·hm⁻²), and D3 (97 500 plants·hm⁻²). The C, N and P contents in maize leaves and soil were measured in different treatments, the stoichiometric ratio and internal stability index were calculated, and the influences of soil environmental factors on maize leaf stoichiometry were analyzed. The results showed that compared with H0, H1 mode significantly increased leaf organic carbon, leaf C∶P and soil organic carbon respectively. Compared with D2 and D3, soil organic carbon, soil total nitrogen and leaf carbon were significantly increased by 10.26%−20.37%, 9.14%−17.49% and 7.83%−18.25% at D1 density, respectively. Among them, compared with H0D3, HID1 significantly increased leaf organic carbon, leaf carbon to phosphorus ratio and soil organic carbon by 21.27%, 14.06% and 25.83%, respectively. The internal stability indices showed that leaf C, N and P internal stability were higher in H1 (complete straw crushing and deep plowing return) mode than in H0 (no straw return), and meanwhile, the highest internal stability of leaf C was observed in the low density (D1) treatment compared with the medium and high density. The internal stability of leaf C, N, and P showed H_C>H_N>H_P, indicating that the plants were more capable of regulating carbon. Correlation analysis showed that leaf C was highly significant positively correlated with soil C and leaf P was significantly positively correlated with soil P. Leaf C∶N was significantly positively correlated with soil C∶N. Soil alkaline dissolved nitrogen was the main factor influencing maize leaf stoichiometry. The composite scores of the affiliation function indicated that the HID1 treatment had the best regulating effect on the internal stability of maize leaf and soil ecological stoichiometry. Under the H1 (complete straw crushing and deep plowing return) mode in the Ningxia Yellow River Irrigation Area, a maize planting density of D1 (67 500 plants·hm⁻²) is favorable for increasing maize leaves and soil carbon, nitrogen and phosphorus contents, and optimizing ecological stoichiometric ratios, which leads to the effective use of soil nutrient resources. This study systematically reveals for the first time the synergistic effects of straw return and planting densities in the Ningxia Yellow River irrigation area.