Abstract: The biodegradation of regular sterane and rearranged sterane in crude oil was studied on the basis of simulated biodegradation experiment to the crude oil.The biodegradation products were analyzed by GC-MS.Research shows that the biodegradation of regular sterane is early than that of rearranged sterane.The biodegradation ability of sterane is C₂7>C₂8>C₂9.Before the great biodegradation of the sterane,those maturity indicators such as isomerization of C₂9 steranes at C₂0 vary slightly.But some biomarker indicators used for the researches on oil-source correlation,oil source and sedimental environment will probably change.These indicators include ratio of regular steran to 17α(H)-hopane,C₂7-C₂8-C₂9 sterane,C₂7-C₂8-C₂9 rearranged sterane,ratio of rearranged sterane to regular sterane,and so on.