Abstract: The complex relationship of oil and water, the origin and distribution of water body of chang8 oil reservoir in Huaqing area of northern Shaanxi province, are the key restricting factors on the development and deployment in this area.Based on the comprehensive analysis of the controlling factors of complex water body, this paper analyzes the genesis of complex water body and establishes a genesis model of water body.The results show that the water distribution of Chang8 reservoir is controlled comprehensively by reservoir structure difference, pore bitumen filling, chlorite membrane-organic complex and reservoir wettability.The water is divided into such genetic types as residual asphalt filling and filling water belt in hyperpermeability zone, local edge and bottom water, retained water of dense lens body in hyperpermeability zone sand body, water body in top mudstone segment without displacement, water body in tight sandstone lens body, and water body in interlayer and interlayer barrier body at the riverway edge.In addition,the main mudstone section of Chang7 is in direct contact with or close to the reservoir of Chang8, with no or a little interlayer.In the process of exploration and development, measures should be taken to adjust the deployment according to the origin of different water bodies.