HVDC has been rapid development in recent years, but the problems of the electromagnetic compatibility of converter valve control circuit are becoming more and more prominent. In order to study the PCB anti-harassment problem, we study radiation coupling mechanism of monitoring circuit board. In order to simplify the model, firstly we study microstrip line using transmission line method, and then create a physical model of monitoring circuit board. Through simulation, we can acquire the induced voltage of the chip pins as well as the distribution of electromagnetic field around.