Food industry is demanding higher and higher quality of frozen food, and the quickfreezer can well meet this requirement. In this study, the internal flow field of quick freezer with slit nozzle type was taken as the research object.Three different sizes of nozzle structures based on inlet pressure of 190 Pa, 170 Pa and 160 Pa, numerical simulation and field test of computational fluid dynamics (CFD) were used to compare the differences of internal flow field and heat transfer characteristics of three nozzle structures under different pressure conditions. The results showed that the outlet wind velocity, Nusselt number and uniformity of slit nozzle T₀ at 190 Pa were better than those at 170 Pa, and the cross-flow wind velocitywas also lower. The exit wind velocity, Nusselt number and uniformity ratio of slit nozzle T₁ at 170 Pa weregood, but the crossing flow wind velocity increased. Compared with T₂, the slit nozzleT₀ had lower cross flow velocity at the same inlet pressure. In terms of heat transfer intensity, when the inlet pressure was 190 Pa, the local Nusselt number of strip surface corresponding to slit nozzle T₁was the largest, while the average Nusselt number of T₀ and T₁was not much different. In terms of heat transfer uniformity, the slit nozzle T₀ had the lowest non-uniformity and the most uniform heat transfer when the inlet pressure was 190 Pa. Therefore, when the mass flow rate of air was the same, the slit nozzle T₀ corresponding to the inlet pressure of 190 Pa could better improve the heat transfer efficiency, and could increase the freezing rate of foods.