Abstract: Based on the Eulerian multiphase flow model, this paper uses numerical simulation to study the effects of key operating parameters such as wet air inlet temperature, cold surface temperature, relative humidity and inlet flow rate on the surface frosting characteristics of the fins of a flat and straight finned tube heat exchanger. The results show that each parameter has a significant and coupled effect on the spatial distribution and accumulation rate of heat exchanger surface frost. Overall, the increase of inlet wet air temperature and relative humidity, as well as the decrease of cold surface temperature and inlet flow rate accelerated the accumulation of frost thickness on the fin surface. Among them, the cold surface temperature was the dominant factor influencing the increase of frost layer thickness: when the cold surface temperature was decreased from −5 ℃ to −20 ℃, the frost layer thickness increased by 32.04%; the inlet flow velocity had the least influence on the frost layer thickness, and the thickness only increased by 12.55% when the flow velocity was decreased from 2 m/s to 0.5 m/s. In terms of frost layer density, the enhancement of wet air inlet temperature was the most significant, and the frost layer density increased by 41.32% when the temperature was increased from −5 ℃ to 5 ℃. The results of the study can provide some theoretical references and data support for the optimal design of frost prevention and defrosting of tube and fin heat exchangers under actual working conditions.