A computer power supplier with a built-in power saving controller has a power input socket connected to external AC power supply. A DC switch circuit is connected to AC power and converts AC into DC. A control switch is connected to the AC power. A computer power supply circuit is connected to the AC power of the control switch and converts the AC into DC. A power output socket is connected to the AC power of the control switch and supplies power to peripheral equipment. A power start-up circuit is connected to the DC power of the DC switch circuit and the control switch, and operates the control switch to transmit AC power. A cluster cable transmits the DC power to the mainframe. A boot button is connected both to the start-up circuit and mainboard, so as to convert the AC into DC for the mainframe and start-up circuit.