An indoor positioning system based on inertial navigation is designed to track indoor pedestrian movements. In this system, the accumulated error in inertial navigation is reduced by the improved zero velocity update, increasing the positioning accuracy of the positioning system to less than 1% mileage. The real-time positioning information obtained by the system is uploaded to the cloud through 4G communication, and the tracks of pedestrian movements are simultaneously drawn and displayed at the user interface. The test is performed in a square-shaped building with stairwells on the opposite sides for fire fighting. The testers equipped with the system enter this building from the first floor, go through a long corridor and then arrive at the stairs in the north. Then they climb the stairs to the third floor and come to the smoke-proof stairwell in the south after a long corridor. From this stairwell, they go down stairs to the first floor and return to the starting position. At this point, the whole process is completed in a closed loop, involving the movements of testers such as walking, trotting, and going up and down stairs. Multiple tests reveal the real-time positioning error is less than 1%, proving the superior real-time autonomous navigation of the indoor positioning system without any auxiliary system.