Abstract: To address the problem of frequent circulation loss during the drilling of the Jimusaer shale oil block, an analysis of the relevant mechanism was conducted from the perspectives of stratigraphic distribution, lithological differences, and reservoir development characteristics. The circulation loss in this block was mainly concentrated in the Jurassic Badaowan Formation and the Permian Wutonggou Formation. The pores were developed in the glutenite of the unconsolidated shallow loss formation, while the induced fractures occurred in the deep loss formation. The circulation loss can be classified into the permeable type and the induced fracture type. Depending on circulation loss mechanism and the experience of dealing with it in the Jimusaer shale oil block, the matching principle between plugging materials and the circulation loss rate was formulated, and prevention and control countermeasures were proposed. As a result, the technology to prevent and control circulation loss was developed for the Jimusaer shale oil block. It reduced the incidence of circulation loss from 38.00% to 19.70% and enhanced the success rate of plugging to 75% in the block. This indicates that the proposed technology is effective for tackling the problem of frequent circulation loss in the Jimusaer shale oil block, and can provide technical support for the development of this block.