Abstract: A large amount of straw has been an agricultural resource in recent years. Straw returning mode can also determine the soil fertility and wheat yield. Among them, grain filling is one of the important influencing factors on wheat yield. This study aims to reveal the effects of straw returning mode on the grain filling of winter wheat in sand ginger black soil. The 15a long-term positioning experiment was carried out at the Crop Cultivation Scientific Observation Station in East China of the Ministry of Agriculture and Rural Affairs. Yannong19 was taken as the research object. Four modes of straw returning were set, namely, single-season wheat straw total crushing mulching and returning to field (T1), wheat straw total crushing and mulching and returning to field + corn straw total crushing and burying to field (T2), single-season corn straw total crushing and burying to field (T3) and wheat-corn straw no returning to field all year round (CK). Richards equation was used to simulate the grain filling of winter wheat. Different modes of straw returning were regulated on the filling characteristic parameters for the superior and inferior grains of winter wheat. The results showed as follows: 1) Compared with non-returning straw, straw-returning treatment increased the grain volume, 1000-grain weight, and yield of superior and inferior winter wheat. The 1000-grain weight and grain yield of superior grain under T1, T2, and T3 treatment significantly increased by 11.02%, 10.63%, 13.75%, and 16.28%, 14.29% and 13.94%, respectively, compared with the CK. The 1000-grain weight and grain yield of inferior grain significantly increased by 9.73%, 6.64%, 7.57% 19.24%, 23.25%, and 11.50%, respectively. Richards equation was performed better to simulate the grain filling of winter wheat under straw returning. The coefficient of determination (R²) of the fitted equation was above 0.997. 2) In the superior grain of winter wheat, straw returning to the field also prolonged the filling time of the superior grain of wheat, thus shortening the duration of the gradual filling period. The filling rate increased to extend the duration of the slow filling period for the increase in the 1000-grain weight of superior grain. The filling duration of superior grain under T1 and T3 treatments was 2.137d and 4.443d longer than that of CK, respectively. The maximum filling rate of superior grain under T1 and T2 treatments significantly increased by 7.81% and 12.26%, respectively, compared with the CK. 3) For an inferior grain of winter wheat, the filling time of inferior grain under T1 treatment was 1.477 d longer than that of CK, and the maximum filling rates of inferior grain in T1, T2, and T3 significantly increased by 16.46%, 22.69%, and 17.13%, respectively, compared with the CK. Therefore, the total straw returning increased the grain storage and grain filling rate of winter wheat in the area of sandy ginger black soil. Finally, there was an increase in the grain weight. The finding can provide theoretical guidance and technical support for the efficient utilization of straw resources in sand-ginger black soil areas.