Abstract: As the main controlling factors of hydrocarbon accumulation in Chang 4+5 oil layers of HX area are unclear,there will be bad impact on screening the favorable areas on subsequent exploration and development.Based on drilling,well testing and logging data,combined with previous regional structure study results,the research on reservoir characteristics and its main controlling factor of hydrocarbon accumulation in Chang 4+5 oil layers of HX area has been firstly carried out.The results show that lithologic reservoir is the main oil reservoir type,with smaller single reservoir scale,more single reservoirs longitudinally laminated,staggered and spliced to form more scatted oily favorable areas.The differences of reservoir physical properties are obvious,and the reservoir physical property in the south is superior to that of in the north.There is no correlation between permeability and test oil production.The source rocks distribution is of certain control on Chang 4+5 reservoir,and there is a preferential migration passage at the basement fracture and the around area,which is the main controlling factor of hydrocarbon accumulation and determines the oil reservoir distribution.Therefore,the subsequent exploration and development work should focus on and near the basement fracture zone.