The research aimed to elucidate the varying trends of seedling quality and grain yield，and the mechanisms of strong seedling cultivation under long-term straw return and nitrogen application.Based on the 16-year long-term positioning experiment，the main factor was straw returning (T) and no-returning (S)，the secondary factor was total nitrogen application of wheat and maize，including 0 kg/hm² (N1)，360 kg/hm² (N2)，450 kg/hm² (N3)，540 kg/hm² (N4)，630 kg/hm² (N5)，and 720 kg/hm² (N6)，to analyze the characteristics of grain yield，and the growth and physiology of seedling under long-term straw return and nitrogen application.The results showed that compared with no straw returning，long-term straw returning significantly increased grain yield，stem and tiller number，tillers per plant and dry matter accumulation (DMA) per stem during the overwintering stage，and as straw returning years increased，grain yield，stem and tiller number，and tillers per plant increased by an annual average of 12.75 kg/hm²，9.22×104/hm² and 0.019，respectively，while the annual reduction of DMA per stem，in the straw returning was 0.34 mg lower than that of no returning.The yield and DMA per stem at the overwintering stage of N4 were significantly higher than those of other low nitrogen treatments，reaching 8602 kg/hm² and 134.74 mg，respectively.The stem and tiller number and tillers per plant of N5 showed the same pattern as previous one，and the yield，stem and tiller number and tillers per plant at the overwintering stage did not significantly increase with more nitrogen，while DMA per stem decreased.Mainly，compared with SN4，except for nitrogen accumulation per stem，TN4 significantly increased soil organic matter，alkali-hydrolyzale nitrogen，available phosphorus and available potassium content，root length density and root weight density by 0.75 cm/cm3 and 0.38 mg/cm3，and promoted dry matter synthesis (sucrose synthase，sucrose phosphate synthase and sucrose content) and tiller development.Although more nitrogen application under straw return increased the alkali-hydrolyzable nitrogen content，root length density，and root weight density，and stem and tiller number，it decreased available phosphorus，available potassium content in the soil，as well as sucrose synthase activity，sucrose phosphate synthase activity，and sucrose content in aboveground.Thereby，individual growth was weakened.The yield was significantly positively correlated with stem and tiller number，tillers per plant，and DMA per stem during the overwintering stage.In conclusion，while long-term straw returning improved soil nutrient content，root growth，and tiller number of seedlings，it also reduced individual matter accumulation.Therefore，it can be combined with an appropriate amount of nitrogen (N4) to increase the aboveground sucrose synthesis capacity and the DMA per stem of seedling，to create the groundwork for high-yield wheat.