Abstract: To further explore tillage practices for improving soil structure, the effect of different tillage practices on the structure and organic carbon of tilth soils were investigated using routine method (Wet-sieving, Potassium dichromate volumetry and Core-cutting sampling). The 7-year research was conducted at an experimental station in the semiarid Loess Plateau zone in central Gansu Province. The conservative management practices of no-tillage (NT), conventional tillage with straw incorporation (TS) and no-tillage with straw mulch (NTS) increase soil organic C and water-stable soil aggregates contents, with the highest effect under NTS tillage. Soil bulk density decreases while soil porosity increases, greatly improving soil structure under NTS in the 0~10 cm soil layer. Content of soil water-stable aggregate (1~0.5 mm) is the highest in all 3 soil layers, 0~5 cm, 5~10 cm and 10~30 cm. Soil water-stable aggregate (>0.25 mm) has a significant positive correlation with soil organic C content and porosity, but is significantly negatively correlated with soil bulk density.