Carbon isotopic (δ13C) stratigraphy is widely applied on researches of global carbon cycle,bioevents of mass extinctions and stratigraphic division and correlation.Whether δ13C data of samples present primary of paleoenvironment or altered under diagenesis were well discussed,however,these discussions were under investigations of samples characteristics,and without mechanisms and enough evidences on microbiology which widely exists in normal environment.This article designed a laboratory experiment to study possible changes of carbonate δ13C under a simulated anoxic marine benthic environment where organic material and microbes exists.