The invention provides a cruise control system controller low in cost and high in security and a control method of the cruise control system controller. According to the cruise control system controller, a vehicle-mounted standard equipped part and commonly used control and sensor signals are combined, an electronic accelerator pedal signal is limited into an accelerator pedal signal adaptive to the cruise speed through a control chip after a cruise switch is turned on, the accelerator pedal signal is transmitted to a vehicle ECU, the maximum speed is controlled in the mode of simulating the travel of an accelerator pedal, and cruise control is completed. When the cruise control system controller is applied, the structure of a part body does not need to be disassembled or modified, what is only needed is to modify corresponding wiring harnesses and add a few control and display devices, existing vehicle models with high parc are easy to refit, front loading of a vehicle factory is facilitated, and much cost can be saved; when an accident or breakdown happens to a system, a circuit is disconnected in a physical way, and good security and reliability are achieved.