Joint control of speed and traffic timing based on Vehicular Ad Hoc Networks(VANETs) is one of the core technologies in intelligent transportation system. Therefore, VANETs-based Vehicle Speed Controlling Optimization(VSCO) scheme with traffic light is proposed. VSCO scheme optimizes the time of traffic lights(green, red and yellow) through VANETs, and plans the vehicles driving by the traffic lights to eliminate Yellow-Light Dilemma(YLD)-related traffic accidents occurring at intersections, reduce CO2 emissions and shorten the waiting time of vehicles. Simulation results illustrate that the proposed VSCO scheme can effectively decrease the waiting time and cut CO2 emissions, compared with conventional scheme referring to traditional traffic light using fixed signal control method.