Numerical simulation of temperature and velocity field is carried out on a freezer based on PHONEICS code.The physical and mathematical models are established by suitable geometric simplifying. The effect of the moving of the transmission belt,the inlet velocity and inner flow field with different height of channel and angle of incidence are analyzed.It is indicated that the selection of the inlet velocity and height of channel should be under the combinated consideration of magnitude,uniformity of air velocity along the transmission board and resistance loss of air flow.The best angle of incidence is zero.