The main circuit of Buck converter is analyzed in CCM mode, and the small signal model is derived in detail. Three kinds of closedloop control compensation networks have been designed and named PD, PID and the “doublepole and doublezero” compensation networks. This paper derived the system of the openloop transfer function after compensation network, and simulated the Bode plot of the openloop transfer function before and after the compensation network in matlab. The results indicated that the phase margin was 51.5 degrees, the steadystate error was zero, and the down frequency of amplitudefrequency characteristics was 40dB/dec at high frequencies after“doublepole and doublezero” compensation network. The results had better stability and dynamic performance, and better suppress in high frequency interference. The result has a very good reference for further research of other switching power supply.