Abstract: The oil and gas maturity,hydrocarbon migration and accumulation in the west of north slope in Gaoyou Sag are discussed according to such geochemical parameters as steroid,terpane,light hydrocarbon and nitrogen compounds in this paper.Researches show that the oil in Matouzhuang area is low-mature to immature,the oil in Chian area is mature.The oils trapped in Wei 5 Block and Wei 8 Block are biodegraded.The petroleum in the two areas come from different oil sources.The parameters of light hydrocarbon migration show that the hydrocarbon in Chian area comes from Shaobo Subsag.The parameters of nitrogen compounds migration indicate that the hydrocarbons in Chian area migrate from east to west and the hydrocarbons in Matouzhang area migrate from south to north.