Abstract: The paper took speed regulation system of switched reluctance motor with 8/6 structure as object of study, analyzed influence of state of switched reluctance motor on H-bridge chopper switch under condition that rotate speed is closed loop, and gave calculation method of voltage power spectrum of chopper switch in two kinds of chaotic state. It proved effectiveness of suppression of electromagnetic interference by chaos with nonlinear simulation model of switched reluctance motor and method of getting probability density distribution by eigenvalue, and calculated voltage power spectrum of chopper switch under two conditions by composite Simpson formula. The simulation and experimental results approximately agree with theory analysis results, confirm that chaos has great potentiality in improving electromagnetic compatibility of power transmission system.