Abstract: Explosion-proof diesel engine is one of the most widely used power sources for auxiliary transportation vehicles in coal mines at present. It is affected by explosion-proof transformation and harsh underground environment, resulting in serious exhaust pollution, which is contrary to the green mine development strategy. The emission standard of Non-road National Stage III has been implemented in coal mine since December 2020, but at the present stage, the exhaust gas purification of explosion-proof diesel engines for mining uses the internal pretreatment technology, which cannot meet the emission requirements of the Non-road National Stage IV and higher standards. Aiming at the problems of serious exhaust pollution and lagging exhaust purification technology, a four-element combined exhaust aftertreatment system was designed. Through simulation and bench test, the structural parameters optimization of key components and the purification performance of exhaust were studied. First of all, according to the explosion-proof requirements of underground coal mines, a four-element combined exhaust aftertreatment system of explosion-proof diesel engine composed of Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF), Selective Catalyst Reduction (SCR), and Explosion-proof & Temperature Control device（EPTC） was designed, which exceeds the Non-road National Stage IV standard. The heat transfer analysis of EPTC device structure was carried out through the STAR-CCM+ software. The results show that the pipe wall temperature is less than 150℃, which could meet the explosion-proof requirements of coal mine safety regulations. Then, taking a 60 kW explosion-proof diesel engine as the research object, the simulation models of DOC, SCR and DPF aftertreatment components were built based on the GT-Power software. The key structural parameters and purification performance of the aftertreatment system were optimized by orthogonal test, and the optimal structural parameters of the key components were determined, and the following rules were obtained. The purification efficiency of pollutants increases with the increase of carrier diameter, carrier length and channel density of DOC and SCR. The effect of carrier length and diameter on the capture efficiency of DPF is consistent with the laws of DOC and SCR. Due to the special wall flow carrier structure of DPF, the capture efficiency of PM particles can always be maintained around 96% as the channel density increases. On this basis, the coupling model of the explosion-proof diesel engine and the aftertreatment system was established, and the simulation test of purification efficiency, power and economy of exhaust pollutants from explosion-proof diesel engine was carried out. Finally, a prototype of exhaust aftertreatment system was developed and bench test was carried out. The purification efficiency of the system for CO, NO, HC and particulate matter is greater than 95%, 90%, 83% and 95% respectively, which could meet the requirements of the Non-road National Stage IV standard. The overall output torque of explosion-proof diesel engine equipped with exhaust aftertreatment system decreased by 4.83% on average, and the overall fuel consumption rate increased by 1.19% on average, which had little impact on the power and economy of explosion-proof diesel engine.