Abstract: In order to research the effects of soil tillage patterns on decomposition of returning crops straw in wheat/maize farmlands of the irrigated high-yield farmland, four tillage patterns were adopted in Longkou city, Shandong Province, China for a whole year including winter wheat and maize growth seasons. Four tillage patterns were as follows: conventional tillage with straw returned (CS), rotary tillage with straw returned (RS), disk harrow tillage with straw returned (HS), no-tillage with straw covered (NC). Decomposition rate, decomposition speed and cellulose content of the returned straw were investigated. Results showed that the decomposition speed of the returned straw and soil temperature had a significant correlation; there was no significant difference between the decomposition rate of returned straw of RS, HS and CS, and it was the same case with decomposition speed of returned straw. Those phenomena showed that the two minimum tillage patterns (RS and HS) had not reduced straw decomposition because of reduced tillage compared with conventional tillage (CS). While decomposition rate and decomposition speed of returned straw of NC were significantly lower than those of CS, RS and HS. After the wheat growth season and maize growth season, 37.78% of the returned straw whose cellulose content was 20.69% was still remained, which may affect the emergence of wheat in the next year.