To investigate the effect of ventilation tube spacing on refrigerated warehouse floor antifreezing mechanical ventilation system, a steady three-dimensional mathematical model of heat transfer is built in this paper, and the calculational conditions of the heat transfer model are defined according to the heat transfer process and reasonable simplification. The temperature fields of this system are simulated and calculated by CFD software PHOENICS under different kinds of working conditions, such as the mechanical ventilation system isn’t circulating, and the mechanical ventilation system is circulating with different ventilation tube spacing. The results show the advantages of the refrigerated warehouse floor antifreezing mechanical ventilation system. They also indicate the greater effect of ventilation tube spacing on thermal performance of this system. It is pointed that the proper tube spacing is 2.0m