Measurement uncertainty assessment of spaceborne equipment’s power line conducted emission is very complex. Based on analysis uncertainty sources of the power line conducted emission measurements from 10 kHz to 10 MHz(CE102), taking a spaceborne equipment as test equipment, measurement uncertainty methods of CE102 is studied. Firstly, the measurement principle of CE102 is introduced. On the basis of analyzed the measurement principle, the main uncertainty source including the measurement repeatability, instrument’s measurement performance and impedance mismatch,et al, is determined. Secondly, mathematical model of measurement uncertainty is established, and standard measurement uncertainty of each component is assessed. Finally, the expanded uncertainty of CE102’s measurement results is calculated by GUM method. The results show that the expanded uncertainty of a spaceborne equipment’s CE102 measurement results is 2.7 dB. The results give a positive effect for the EMC measurement systems development in laboratory building, improve the laboratory measurement capability and protect the quality of the measurement results, and it has important reference value for the CE102’s measurement uncertainty assessment of electronic equipment on other military platform.