The embodiment of the present invention discloses a method and system for obtaining optimal vehicle efficiency, wherein the method includes: establishing a force model of the vehicle; sampling the speed of the vehicle to obtain feedback data, and obtaining driving resistance according to the force model of the vehicle Equivalent coefficients A, B, C; according to the equivalent coefficients A, B, C of driving resistance and the mass of the vehicle, determine the required torque of the vehicle; set the torque interval to filter the motor high-efficiency point to output the optimal torque to realize the vehicle optimal efficiency. This scheme establishes the mathematical model of the whole vehicle, and uses the equivalent force coefficient of the whole vehicle in the closed-loop adjustment to meet various working conditions in the operation of the whole vehicle. Optimize the calculation method, look up the table, difference, weight, advance calibration and other methods to improve the calculation efficiency.