The invention belongs to the field of power and electron technology, and provides a system and a method for controlling a Buck converter based on phase path planning and tracking. PWM control is carried out on a switch element in the Buck converter by a controller, and the controller is internally provided with a load recognizer, a path planning device, a supervising device, a path prediction controller, a PI controller, a selector and a digital pulse-width regulator; the load recognizer is used for detecting the load parameter of the Buck converter; the path planning device is used for establishing a state model and planning a phase path of the Buck converter; the path prediction controller is used for detecting an inductive current value, and comparing with a prediction planning inductive current value to realize tracking control for dynamic paths; the supervising device is used for outputting a control strategy switching signal; the PI controller is used for realizing steady tracking; the selector is used for selecting a control strategy; and the digital pulse-width regulator is used for driving the switch element in the Buck converter to realize the PWM control. According to the system and the method, quick response for the Buck converter and accurater control for the Buck converter are realized.