The abnormal communication and PCB burning will occur due to the continuous flashing of the discharge-tube in the DC monitoring system in the PV power generation station. Thus this paper elaborates how to find the problem, make an analysis and shoot the troubles. Through the analysis of the test waveform, the coupling channel of the interference source, the communication lightning protection circuit of the PCB and so on, it concludes that accident is mainly caused by the common-mode voltage in the inverter switch-tube has not been effectively restrained during runtime. After the transformation of the grounding circuit of the equipment, through test and verification, the problem is effectively solved. In order to suppress common mode voltage and improve system performance, it is necessary to design and test the relevant equipment and EMI strictly before the photovoltaic power station is put into operation. This work is supported by Science and Technology Project of State Grid Corporation of China (No. 5292C0140113).