Abstract: In order to improve the milling efficiency of packer grinding sleeve in the process of offshore workover, and ensure the reliability and economy of the operation. By studying the main factors affecting the milling efficiency of the grinding sleeve, the screw drilling tool with a single head hydraulic motor was specifically introduced, and the structure of the grinding sleeve milling string was optimized with downhole tools such as the fishing cup and the jar. Based on this condition, the design method of key construction parameters was optimized synchronously, and a set of offshore oilfield screw drilling tools was formed to improve the milling efficiency of the workover packer. This study has been applied in the workover process of BX Well in the 12-1 Oilfield in Beibu Gulf of the western South China Sea. Compared with conventional operation methods, it improves the drilling efficiency by nearly 10 times, and the speed and efficiency are significantly improved, which provides good reference for improving the efficiency of grinding sleeve milling in subsequent offshore workover.