Abstract: 【Objectives】 Study on the effect of different mulching treatments on soil aggregates and their relationships with soil organic carbon, will help selecting the sustainable mulching measures for the loess hilly region of China. 【Methods】 The field experiment was carried out in 2008. Four treatments were included as control without mulching treatment (CK), straw mulching at a rate of 9000 kg/hm2 (M1), straw mulching at a rate of 4500 kg/hm2 (M2) and plastic film mulching (PM) during winter wheat growing season. Soil samples were collected at layers of 0-10 cm and 10-20 cm in 2014 after crop harvest, soil aggregates were separated into 5 mm, 5-2 mm, 2-1 mm, 1-0.5 mm, 0.5-0.25 mm and 0.25 mm and were determined by using dry sieving method and wet sieving method. The mean weight diameter (MWD) and geometric mean diameter (GMD) were calculated and the content of soil organic carbon was also measured. 【Results】 1) Compared with CK, soil mechanical-stable macroaggregates content was increased by straw mulching, the increase in the 0-10 cm soil layer was 5.1% in M1 and 2.0% in M2 treatment, respectively. Both straw and plastic film mulching improved the macroaggregate contents in 10-20 cm soil layer, with significant increase of 7.6%, 4.3% and 3.1% in M1, M2 and PM, respectively. 2) Compared with CK, the contents of water-stable macroaggregates (0.25 mm) in M1 and M2 were increased by 6.8% and 5.0% in 0-10 cm soil layer, respectively, mulching with plastic film had no significant effect. 3) All the straw mulching and plastic film mulching treatments improved the values of MWD and GMD in 0-10 cm soil layer significantly. Compared with CK, the soil MWD was increased by 47.8%, 24.7% and 24.6%, and the GMD was by 48.9%, 34.8% and 31.6% in M1, M2 and PM treatments. 4) Soil organic carbon content was increased by straw mulching. Soil organic carbon content was in turn 11.9% and 6.3% higher in 0-10 cm layer, and 4.2% and 4.5% higher in 10-20 cm layer in M1 and M2 than in CK, respectively. Plastic film mulching had no effect on soil organic carbon sequestration. Soil organic carbon content was significantly correlated with 0.25 mm size water-stable aggregates content at 0-10 cm depth. 【Conclusions】 In the perspective of soil structure, mulching with crop straw rather than with plastic film could improve soil structures and soil quality through increasing the quantity of water-stable macroaggregate and total soil organic carbon content. Straw mulching at a rate of 9000 kg/hm2 is superior to other rate and can be regarded as a reasonable cultivation practice in the Loess Plateau.