Abstract: A displacement method of chromatography for analysis of group composition of light crude oil and condensate was introduced in the paper.The samples were filled into chromatographic columm,silica gel was used as stationary phase,and ethanol was used to replace the hydrocarbon adsorbed by silica gel.Hydrocarbon composition moved out in different time were determined according to their refractive index(RI).Volumes of various group composition were calculated by using addible RI of hydrocarbon mixtute,then their volume percentage was determinded.This method may be applied to analysis of light composition of heavy oil.