The current transmission simulation load spectrum is difficult to fully reflect the load state of the transmission gear because of considering driver’s intention is not fully. In order to improve the accuracy of transmission reliability analysis, a mining vehicle equipped with a 12 speed gearbox is taken as the research object. Based on the shifting rules of power and economy, a multi speed transmission simulation load spectrum acquisition method considering gear combination strategy is proposed by fully considering the allowable gears of different vehicle speeds. based on the driver conditions of mining vehicle, the proposed method was used to obtain multi-speed transmissions simulation load spectrum, and compared with the simulation load spectrum obtained based on power and economic shifting schedule. The result show that compared with the traditional method of obtaining load spectrum based on shifting schedule, the method was proposed obtain different dangerous gears. The dangerous gear obtained by traditional method is 6th gear, with a working time accounting for 53.25%, the proportion is highest in the load range of 2000~2400N.m, with 53.14%. the method was proposed obtain the dangerous gear is 7th gear, with a working time accounting for 54.49%, the proportion is highest in the load range of 2400~2800N.m, with 52.78%. From the perspective of load accumulation, it can be observed that the load accumulation of the proposed method obtain 7th gear increases 2.33% compared with the load accumulation of the traditional method obtain 6th gear. The research result prove the effectiveness of the proposed method and lay the foundation for the reliability design of multi-speed transmissions.