A method for calculating efficiency of a power supply system includes: displaying a parameter selection interface on the display unit for selecting power supply parameters and transmission line parameters. Obtaining power supply parameters and transmission line parameters selected by the user via the parameter selection interface when determining the user has finished the selection. Determining a efficiency of a selected power supply of the power supply parameters according to the relationship table, and calculating a sum efficiency according to the obtained power supply parameters and the transmission line parameters and the efficiency of the selected power supply. And calculating a total efficiency of the power supply system according to each sum efficiency when determining that all of the power supplies of the power supply system have been selected.