With the improvement of people’s living standard, the requirements of indoor air environment are also increased correspondingly. Trombe wall can not only improve the natural ventilation of buildings but also play an important role in cooling and heat storage of indoor temperature. The study of air flow velocity in Trombe Wall is critical for the improvement of Trombe wall performance. In this study, the regular patterns of air velocity is derived and analyzed by combining mathematics and simulation. And the changing rules of air velocity under different conditions are obtained. These research results can provide reliable basis and good reference for Trombe wall design and natural ventilation analysis. •Trombe wall should be the same width as the boundary line.•The air velocity can be controlled by changing of the wall height.•The air velocity also increases with the increase of temperature difference.