Abstract: To enhance the fuel economy of light trucks under complex working conditions, a method based on narrow-domain optimization was studied. A power-split hybrid power system and its control strategy suitable for light-duty trucks were designed and implemented. The engine operating speed was actively controlled within a narrow and efficient range. Through conducting comparative tests with traditional manual transmission light trucks （prototype vehicles） under actual road conditions, the differences between the prototype vehicle and the power-split hybrid modified vehicle in terms of comprehensive fuel consumption, distribution of engine operating points, motor working characteristics and energy recovery efficiency were systematically analyzed. The test results show that the combined fuel consumption of the power-split hybrid light truck under the combined working conditions of urban area, suburban area and high-speed is 0.100 2 L/km, which saves 17.37% of fuel compared with traditional vehicles. Among them, the fuel-saving rate in urban area working conditions exceeds 30%. The engine operating points are concentrated in the high-efficiency zone of 1 300~1 600 r/min, and the regenerative braking energy recovery efficiency exceeds 65%. The power-split system has a significant fuel-saving effect on light trucks. However, overly pursuing the operation of a single high-efficiency zone of the engine may reduce the overall energy efficiency of the system.