The current gearbox simulation load spectrum is difficult to fully reflect the load state of the gearbox gear, because driver’s intention is not fully considered. In order to improve the accuracy of gearbox reliability analysis, a mining vehicle equipped with a 12 speed gearbox was taken as the research object. Based on the shifting rules of power and economy, a multi-gear gearbox simulation load spectrum acquisition method considering gear combination strategy was 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-gear gearbox 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 proposed method obtains different critical gears. The critical gear obtained by traditional method is 6th gear, with a working time accounting for 53.25%, and the proportion (53.14%) is the highest in the load range of 2 000 N?m~2 400 N?m. The proposed method obtains the critical gear is 7th gear, with a working time accounting for 54.49%, and the proportion is the highest (52.78%) in the load range of 2 400 N?m~2 800 N?m. From the perspective of load accumulation, it can be observed that the obtained 7th gear load accumulation of the proposed method increases 2.33% compared with the obtained 6th gear load accumulation of the traditional method. The research result prove the effectiveness of the proposed method and lay the foundation for the reliability design of multi-gear gearbox.