Abstract: Characteristics of 3-stage cooling in oil vapor recovery system worked based on condensation method are summarized. Cascade refrigeration cycle is adopted between the 2nd stage and the 3rd stage, and partial cooling load of the 3rd stage is regulated to the 2nd stage to increase cooling efficiency. Characteristic of structure of fin-type heat exchanger worked based condensation method in oil vapor recovery is discussed and relative parameters of vapor compound such as mean density, mean heat capacity, mean dynamic viscosity and mean thermal coefficient as well as amount of heat exchange of steam phase transformation are calculated. Relationship between inlet flow rate of oil vapor, heat flux density and volume of heat exchanger is investigated. It is pointed out that there exists an optimal inlet flow rate of the oil vapor in structure design of the exchanger. Research results are considered as reference value on the design of the exchanger.