Focused on the issue that the integrated position system was made of WiFi positioning system and strapdown inertial navigation system was very complex and difficult to implement in engineering, a new reducedorder ten d state variables integrated positioning system of a simple micro inertial measurement unit(MIMU)which was composed of the low precision micro inertial sensors and WiFi was proposed. The simple installation structure of MIMU was designed by one low precision micro gyroscope and two low precision micro accelerometer inertial sensor pieces, then it was combined with WiFi location system and Kalman filtering technology was applied to integrated navigation positioning algorithm. The simulation results show that the proposed reducedorder integrated positioning system positioning calculation dimension reduction reduces computational complexity and makes it easy to complement in engineering, meanwhile effectively improves the downhole positioning accuracy, which can be effectively applied to the underground personnel positioning problem.