The invention discloses a vehicle speed control system and method of a ramp merge area, and belongs to the field of road traffic control. The system comprises a vehicle-mounted communication device and a roadside control unit; the vehicle-mounted communication device collects vehicle motion information and sends the vehicle motion information to the roadside unit; the road side unit receives information of all vehicles within a control area, makes decision in a concentrated way, manages and controls time when vehicles reaching a merge point in a unified way by utilizing a vehicle time regulation method within the area, forms vehicle behavior control rates in the area according to a time control requirement by utilizing a vehicle behavior optimized control method, and sends the control rateto each vehicle so that the vehicle can arrive at the merge point on time according to the received control rate. A vehicle and road concentrated communication technology is used, vehicle merge timeis controlled and vehicle merge behaviors are optimized in the control area, so that merging with high efficiency and comfort level and low oil consumption is realized for vehicles in the ramp area.