Abstract: Due to the problem of behavior failure or functional safety for electronic system caused by electromagnetic interference (EMI), the electromagnetic susceptibility characteristics of programmable integrated circuit (IC) based on the conducted coupling of power supply network are studied. The topology structure of power supply network and the EMI conducted coupling mechanism of typical FPGA are analyzed, and the immunity test platform based on EMI direct power injection method is designed. The electromagnetic susceptibility feature of typical functional units are measured when the EMI is conducted to the power supply network of the IC under test, then the susceptibility thresholds of internal phase-locked loop (PLL) circuit, logic element (LE) and input/output port is obtained and the influence law of LE redundancy design on EMS characteristic of corresponding circuits is given. The results show that, for interference frequencies in the range of 10 MHz-1 GHz, functional units with EMI susceptibility from high to low are PLL, LE and IO, and the EMI susceptibility of IC ground network is 2-7 dBmW higher. LE redundancy design can effectively improve the EMS of logical functional units.