Aims This study investigated the dose‐effect of manganese (Mn) addition on wheat straw (WS) decomposition, and explored the potential mechanisms of Mn involved in the acceleration of WS decomposition in regards to the soil microbial communities and enzyme activities. Methods and Results A 180‐day incubation experiment was performed to examine the decomposition of WS under four Mn levels, that is, 0, 0.25, 1 and 2 mg g−1. The effects of microbial communities and enzyme activities were evaluated using control (0 mg g−1) and Mn (0.25 mg g−1) treatments. Our results revealed that Mn (0.25 mg g−1) addition significantly increased WS decomposition, and enhanced the release of carbon and nitrogen. Optimal Mn addition (0.25 mg g−1) also caused significant increases in the activity of neutral xylanase (NEX), laccase (Lac), manganese peroxidase (MnP) and lignin peroxidase (LiP) within the incubation period. Mn (0.25 mg g−1) addition also enriched some operational taxonomic units (OTUs) that, in turn, had the potential ability to decompose crop straw, such as secreting lignocellulolytic enzymes. Conclusions Mn (0.25 mg g−1) could promote WS decomposition through enrichment of the microbial species involved in biomass decomposition, which enhanced the lignocellulose‐degrading enzyme activity. Significance and Impact of the Study This study provides evidence for Mn to promote WS biodegradation after Mn application, opening new windows to improve the utilization efficiency of crop residues.