In the thesis, a software-based digital control using digital signal processor is applied to a multi-phase synchronous buck converter to carry out the task of current-sharing and output voltage control. In addition, the loaded current is automatically monitored in order to adjust the amount of paralleled power stages and the switching frequency of power MOSFET for assuring the converter in highly efficiency. The reliability of converter will be enhanced by redistributing the loaded current to each phase or starting up the backup module when malfunctions occur. The mechanism of multi-phase synchronous buck converter is explained in first. A DSP(dsPIC30F2023) is the central control unit in use to carry out the tasks of current sharing, monitoring of the loading current, and the setting of the amount of the paralleled power stages.