[Objective] To study the effects and mechanisms of long-term no-tillage and straw mulch on soil quality.[Methods] With comparing the soil characteristics from 2001 to 2011, the conventional tillage, no-tillage, conventional tillage + straw mulch and no-tillage + straw mulch were set for 10 years in a corn-wheat-soybean rotation system. Soils of 0-200 cm layers were taken for analyzing organic carbon(C), total nitrogen(N) and total phosphorus(P).[Results] Long-term no-tillage improved C and N contents of surface soils, and straw mulch only had little effect on them. Long-term conservation tillage had no significant effect on soil P level. Conservation tillage resulted in the lowest N and P contents at 20-30 cm soil layer, while under conventional tillage, it was at 30-60 cm layer. Soil C/N, C/P and N/P were generally lower than that of a decade ago and with soil depth increased, the variation of C/N, C/P and N/P showed a drop-rise trend.[Conclusion] Long-term conservation tillage had no significant effect on soil C, N and P. In the four tillage patterns, soil C/N, C/P and N/P were generally lower than a decade ago.