Abstract: Soil stratified sampling method and potassium chemical fractionation analysis were used to investigate effects of long-term shallow tillage and straw returning on soil K contents and stratification ratios in winter wheat/summer maize rotation system in Guanzhong Plain of Northwest China. The results showed that after 13-year continuous shallow tillage and straw returning, surface accumulation and stratification effect obviously occurred for soil available K (SAK) and nonexchangeable K (NEK), which was particularly remarkable for SAK and its fractions. Serious depletion of SAK occurred in 15-30 cm soil layer, and the SAK value was lower than the critical value of soil potassium deficiency. Meanwhile, significant differences were found between SR₁ and SR₂ values of SAK and its fractions, SR was obtained by values of topsoil layer (0-5 cm) divided by corresponding values of lower soil layers (5-15 cm layer, SR₁, or 15-30 cm layer, SR₂). However, no significant difference was observed between SR values of NEK and mineral K. In conclusion, returning of all straw  over 10 years  in the winter wheat/summer maize rotation system contributed greatly to maintaining soil K pool balance, while special attention should be paid to the negative effects of surface accumulation and stratification of SAK on soil K fertility.