In order to decrease the risks of dangerous goods transport vehicles exhaust pipe that temperature of exhaust gas was too high or sparks might light inflammable and explosive materials on the car, ANSYS Workbench platform and Fluent software were used to research the fluid properties and temperature field of four types of muffler assembly structure in a certain type of exhaust pipe of dangerous goods transport vehicle.Four kinds of coolant inlet entrance velocity were selected to make numerical simulation of flow and thermal solid coupling for four different kinds of muffler structure. The results show that when the inlet velocity is 2 m/s, the cooling effect of the C type structure muffler is the best which minimum temperature can be decreased to 8498 ℃.The results provide reference for the cooling structure optimization of the main muffler of the special vehicles exhaust pipe.