This paper introduces the work principle and positioning performance of the transponding navigation system, and gives the navigation and positioning measurement equations. Using two consecutive days of data from the transponding system, the paper analize the performance of User Equivalent Range Error, static positioning accuracy, kinematic positioning and velocity accuracy. The trail show that: the UERE is better than 1.15 m and different satellites shows hierarchical phenomenon. In the constellation state that one IGSO satellite with four GEO satellites, the accuracy of static positioning is better than 4.85 m in horizontal, and 6.3 m in vertical. The kinematic positioning accuracy is better than 12.5 m in horizontal and 13.1 m in vertical, the accuracy of velocity is better than 0.08 m/s in horizontal and 0.12 m/s in vertical, and the repeatability between days is better than 0.01 m/s.