To design the test setup and predict the effect of GJB151B CS115 “impulse excitation bulk cable injection conducted susceptibility”, we introduced the circuit model of inductive pulse current injection for different type of cables. The influences on the injected voltage/current caused by the factors of the test setup are simulated and analyzed. Some regularity characteristics of CS115 test setting are summarized, and the method of CS115 test design and optimization by circuit simulation is proposed.