In order to solve the problem of re-searching and tracking after the loss of test target due to environment and aircraft maneuver in the current model task, we study the structure and principle of real-time telemetry system, and design and develop the system for monitoring situation of multi- target test planes. By introducing the secondary radar data, the system can solve the problem that the situation information of test plane cannot be grasped in time after the PCM signal interruption. In addition, by calculating the relative angle of the aircraft relative to the telemetry antenna, the auxiliary telemetry antenna tracks the test target. The results show that the system plays an important role in ensuring the flight safety of key models.