Abstract: Based on the characteristics of oil/gas occurrence and its genetic mechanism,the paper detailed the controlling factors of the distribution of conventional crudes.It is suggested that conventional crudes are mainly controlled by the following factors,including time of pool-formation,oil/gas source area,conditions of migration and accumulation,and conditions of preservation and structure.Their combined function and affects will determine the regional distribution of conventional cruddes.Of these controlling factors,the thermal evolution of source rocks in source area and the conditions in pool-formation and later preservation are most important.