In order to study the effects of different materials returned to field on soil microbial biomass carbon, nitrogen and microbial entropy of 0-20 cm and 20-40 cm soil layers in summer maize silking and harvesting period, a field experiment was conducted on the purple soil in Sichuan Hilly area. This study was expected to provide a theoretical reference for the comprehensive utilization of agricultural waste organic materials and the improvement of soil quality in hilly areas of Sichuan. Four treatments with different materials returned to field were designed in this experiment, including control (no material returned to the field), faba bean straw, rape straw and pig manure. The results showed that:(1) Although the organic materials were returned to the 0-20 cm soil layer, the soil organic carbon (SOC), total nitrogen (TN), microbial biomass carbon (SMBC), microbial biomass nitrogen (SMBN) contents in both 0-20 cm and 20-40 cm layers were significantly affected. The contents of SOC, TN, SMBC and SMBN in the 0-20 cm soil layer were significantly higher than those in 20-40 cm. Soil SOC, TN, SMBC and SMBN in both soil layers appeared as silking stage>harvest stage during the growth period. (2) In the two growth periods, the three materials returned to the field could increase the SOC, TN, SMBC and SMBN contents of 0-20 cm and 20-40 cm soil layers. Compared with the control, the contents of SOC, TN, SMBC and SMBN in the treatments with materials returned were increased by 2.6%~141.2%, 1.9%~33.0%, 5.1%~114.7% and 41.5%~98.7%, respectively. The contents of SOC, SMBC and SMBN in both soil layers appeared as rape straw > faba bean straw > pig manure > control, while TN contents as faba bean straw > pig manure > rape straw > control. (3) In this study, SMBC/SMBN, qMB and SMBN/TN varied from 3.74 to 10.53, 0.86% to 2.19% and 1.01% to 3.41%, respectively. The materials returned to the field reduced SMBC/SMBN and improved soil qMB and SMBN/TN values. Correlation analysis indicated that there were significantly positive relationships between SMBC, SMBN, SOC and TN. Therefore, we could improve the contents of SMBC, SMBN, SOC, TN and qMB value by returning materials to the field in agricultural production, and then we could maintain high farmland productivity so as to improve soil quality. However, during returning the specific types of materials, the balance among higher soil fertility, maize production and environmental benefits should also be considered.