Aiming at the problem that the sensitivity telemetry parameters of the dual-frequency speed measuring transponder of a rocket-borne TT&C cooperative target are abnormal, the high-precision speed measuring principle of the continuous wave radio external measurement system is studied. According to the actual flight trajectory programming， the antenna pattern of four points relative to the dual-frequency transponder receiving is calculated in the ground tracking measurement continuous wave radar system. It can be concluded that under the abnormal sensitivity telemetry parameters during the jump, due to the iterative guidance and dramatic rocket attitude changing, the site of the equatorial angular is larger, which is greatly beyond the dual-frequency radar transponder receiving antenna gain, and the weaker receiving antenna signal will lead to an abnormal jump of the receiving sensitivity at this time. This paper can provide an important theoretical and decision-making basis for the rapid location and trouble shooting of similar problems in subsequent test tasks.