Abstract: In view of problems that current underground personnel positioning has low accuracy, cannot realize real-time global positioning and it is difficult to search and rescue trapped people, a combined underground personnel positioning system based on combination of micro inertial measurement unit (MIMU) navigation technology and WiFi technology was designed, search and rescue scheme based on the combined positioning system after mine accident was given. The system uses reliable position information provided by WiFi to set initial position information of MIMU and adjust position of MIMU, so as to make up shortage of error accumulation with time of MIMU, uses real-time global positioning of MIMU to compensate local positioning of WiFi. Then it employs Kalman filter to fuse information from the MIMU and WiFi for optimal combination processing. The test result shows that the system realizes real-time three-dimensional global positioning for underground personnel and rapid search and rescue, has a certain engineering practical significance.