EIRP is an important performance index of RDSS user receiver. The major uncertainty source of Beidou RDSS user receiver EIRP measurement using RDSS closedloop test system includes power measurement reproducibility and power measurementdeviation of RDSS simulator, inaccuracyof space loss and antenna gain correction.It can effectively improve the accuracy of EIRP testing by using the calibration system consists of a standard gain horn antenna, a standard peak power meter and a Vector network analyzer. After calibrating, the uncertainty of testing EIRP is less than 1.5dB, meets the testing requirements.