Abstract: The explosion-proof EGR cooling system and the explosion-proof Venturi tube are designed according to the principles of heat transfer and hydrodynamics, and the pump is selected.Then the diesel engine is tested on the bench according to the standard, and the rules of NOx, HC, CO and smoke varying with exhaust gas recirculation (EGR) temperature under different working conditions are studied. In view of the emission pollution problem of coal mine underground mine explosion-proof diesel engine, according to the requirements of MT 990-2006 “general technical conditions for mine explosion-proof diesel engine”, the surface temperature of explosion-proof diesel engine should not exceed 150 ℃, the explosion-proof (EGR) cooling system is carried out. Through the analysis of the principle of explosion-proof venturi tube, the selection of explosion-proof electric water pump and the calculation of the heat dissipation of the cooling system, the EGR cooling system was designed to meet the requirements. Then the bench test of the explosion-proof diesel engine and the EGR cooling system were carried out according to the standard, and the effects of NOx, HC, CO and smoke varying with EGR temperature under different working conditions are studied. The results show that with the decrease of EGR temperature at rated speed, NOx emission decreases, CO emission increases, HC emission increases and smoke decreases; load decreases at the same EGR temperature, NO, CO, HC and smoke emission decreases. With the decrease of EGR temperature, NOx emission decreases by 7.4%, 3.3%, the CO increase is 100%, the minimum increase is 0, the HC emission increase is 20%, the minimum increase is 2.7%, and the smoke emission reduction is 20%, the minimum decrease is 0;It is determined that the optimal cooling performance range of the explosion-proof EGR is 70～100 ℃ under the best condition of the exhaust gas emission when the explosion-proof diesel engine is working.