The belt driven starter generator (BSG) system structure, working principle and working mode were introduced, the oil-saving principle of start-stop system, the relationship between idle speed and oil-saving rate, and the relationship between idle time ratio and oil-saving rate were analyzed. According to the driver’s safety, driving habits and comfort, fuel economy and emission, the BSG start-stop system control strategy was formulated, which included engine automatic stopping strategy, engine automatic starting strategy, start-stop system shutdown strategy, and start-stop coordination strategy. The start-stop control parameters threshold values of battery SOC, catalyst temperature, engine water temperature, environmental temperature, and braking system vacuum pressure were set. The strategies were applied to the real vehicle. On the revolving drum, the fuel consumption and emissions were tested in NEDC cycle with the carbon balance method and instantaneous fuel consumption equipment. On the road, the fuel consumption was tested in NEDC cycle and actual road conditions. The test results showed that the proposed control strategy was correct, the threshold value of control parameters was reasonable, and the control strategy satisfied the requirement of idle start-stop function. The revolving drum test results showed that the BSG system could save oil by 4%~5% in NEDC cycle, and it could save oil by more than 12% in city conditions. The BSG vehicle emission met the national V emission standard. The CO and THC pollutants were decreased significantly, and the NO x pollutants were increased slightly. The road fuel consumption test results showed that during the morning rush of the city, the BSG system could save oil by more than 8.1%.