A cruise control system for an electric wheelchair includes: a drive unit for driving the electric wheelchair; a user control unit for transmitting user control signals; a controller selectively operable in a normal control mode for controlling the drive unit such that a speed of the electric wheelchair is adjusted in accordance with the user control signals; and a current detecting unit for detecting a load current of the electric wheelchair and outputting a corresponding current signal. The controller has parameter relation information loaded therein, and is further selectively operable in a cruise control mode for controlling the drive unit with reference to the current signal and the parameter relation information to maintain the speed of the electric wheelchair within a desired speed range.