Abstract: When calculating the heat exchange design of the heat exchanger of the submerged combustion natural gas heating device, there esist a lot of problems in the design work, which is caused by the complexity of the water bath flow and heat transfer. Combined with the actual operation of the first domestic device, the simulation analysis of heat transfer process in water bath of the device was carried out and measured data of the heating device operation is verified by calculation. The maximum flow velocity of the water bath outside the tube is calculated inversely using the classical heat transfer formula. The simulation results intuitively reflect the flow of the water bath inside the water tank and the heat exchange process between the flue gas and the water bath. The results show that: (1) The heat transfer area of the device is reasonably arranged, the bubble breaking effect is better, and the contact area between the high-temperature flue gas and the water bath is enlarged, and the heat transfer between gas and liquid is strengthened; (2) In the heat exchange process, the heat exchanger is flushed by the gas-liquid two-phase flow at a relatively constant temperature, and the heat exchange is stable; (3) The flue gas at the tube wall of the heat exchanger hardly participates in heat exchange; (4) The maximum relative error of the flow rate of water bath for simulation calculation is 8.33%, which provides a reference numerical simulation idea for calculating the water bath flow rate for the subsequent development and design of the submerged combustion natural gas heating device.