The worst case analysis and monte carlo analysis by means of software PSPICE are implemented on a forward exited switch power supply with feedback loop. The analysis results offer a criterion to definite error range of the device parameters. 用电路分析软件PSPICE对带反馈环的正激式脉宽调制(PWM)开关稳压电源进行最坏情况分析和蒙地卡罗分析,为在设计开关电源时确定元件参数的误差范围提供了依据。