Biochar is a continuum of C-rich solid organic material produced by incomplete combustion of biomass and fossil fuel consumption. Biochar is ubiquitous in the environment, and application of biochar to soil has the potential to enhance long-term sequestration of carbon. Biochar plays an important role in global C cycles and considered as a strategy to mitigate global change. However, knowledge of biochar decomposition and the mechanisms responsible for biochar induced priming effect remains limited. It is necessarily therefore to research on factors controlling biochar decomposition and the possible mechanisms for priming effect. Thus, the aim of this study is to review the decomposition of biochar and priming effect. This review includes decomposition of biochar, the effects of climate/incubation, soil characteristics, biochar properties, and disturbances on biochar decomposition. Methods used to measure the priming effect induced by biochar, direction and magnitude of the biochar priming effects and the possible mechanisms for biochar induced priming effect were summarized. Lack of current studies on biochar decomposition and priming effect, and perspectives for incorporating the biochar into soil organic matter and ecosystem models were also discussed.