Based on the faults occurred in measurement system of Yunnan-Guangdong ultra-high-voltage direct current（UHVDC） transmission for many times， composition of Yunnan-Guangdong UHVDC measurement system and the operation logic for time division multiplexing（TDM） bus are introduced. Through the simulation and experiment， the cause suffering from electromagnetic interference（EMI） and the problems existed in anti-EMI measures of DC measurement systems are analyzed deeply. The corresponding solution scheme is given and implemented. Correctness of the solution scheme is verified by the actual fault. Solution scheme can not only enhance the operational reliability of Yunnan-Guangdong UHVDC operation， but also benefit to the anti-EMI design of DC project.