A simulation study has been made by CFD software Airpak of the thermal pressure ventilation of civil buildings with single heat source. With the total calories of the heat source given, and with the area ratio of the upper and lower orifices changing, a thorough analysis has been made of the variation law of such parameters as the height of the neutral surface, the coefficient of effective heat, ventilation rate and residual heat of the thermal pressure ventilation. With the orifice size fixed, a study has been made of the variation of temperature field, flow field, heat source, surface temperature and other parameters of hot pressing ventilation when the horizontal position of heat source changes with the distance between the orifices. Results show that when the top and bottom orifice open areas are similar, the room will have the best thermal pressure ventilation efficiency; when the bottom open area is greater than the top one, the effective heat coefficient m will change at a low range, and with an increase in the area of an orifice, the neutral plane will move toward the greater area orifice. The closer the heat source to the lower orifice, the higher the heat dissipation efficiency will be.