The heat transfer process of unilateral double open indoor thermal press natural convection is taken as a research object. FVM method is used to solve the mass conservation equation and energy conservation equation. Streamlines, isotherms and variations of average Nusselt number Nuav are studied under the conditions of different Ra（Ra=103~106）and different thermal source locations. Research indicates that: with the increase of Ra, indoor air convection intensifies and the convection heat exchange effect is obvious, and with high Ra and increasing D, the indoor swirl appears increasing. In the case of D=0.25, Nuav all reach maximum under different Ra, and the thermal location has great effect on heat exchange. Under the same Ra, indoor heat exchange effect is worse with increasing D, and under different D, Nuav is a power exponent function with Ra as the independent variable, and its linear correlation fitting reaches 96.2%.