The insulated gate bipolar transistor (IGBT) module is a core component of high-power electronic device systems. Since the junction temperature of an IGBT module increases with operation, the junction temperature of the IGBT module is the main cause of failure, which seriously affects the safe and stable operation of systems. To restrain the junction temperature and to improve the reliability of IGBT modules during operation, a new stochastic pulse width modulation (PWM) strategy is proposed. It is deduced that this method can do a good job of restraining the junction temperature of IGBT modules. The effectiveness of this method is verified on an experimental platform of a permanent magnet synchronous motor system. Experimental results show that the stochastic PWM has a good inhibitory effect on the junction temperature of IGBT modules in the same cycle, and that the difference of the most significant inhibition effect is about 3.27 K. The proposed stochastic PWM has practical engineering significance in terms of restraining the junction temperature of IGBT modules.