The sensitivity threshold of differential signal receiving chip(DS26C32ATM) is studied by Pulse Current Injection(PCI) technology. The experimental results show that the injection current on transmission line increases with the increase of pulsed voltage, and the interface circuit of differential signal receiving chip is damaged by electromagnetic pulse interference. The failure mechanism of the damaged chip is analyzed and the fault position is located. Based on the analysis results of failure mechanism, the protection of differential signal receiving chip is studied. The experimental results provide a reliable basis for the experiment of anti-electromagnetic pulse interference.