Abstract: Taking the basement in a residential building as research object, according to window-to-floor ratio of the natural ventilation evaluation index in the Assessment Standard for Green Building, seven kinds of models of working condition in architectural construction were established. Fluent software of computational fluid dynamics was used to simulate and analyze the wind field, air age, air change rate and non-uniformity coefficient under different working condition and all the indexes were compared and evaluated. The optimum scheme of natural ventilation in the underground space of residential building was explored. The results show that the larger the window-to-floor ratio is, the better the indoor ventilation effect is. At the same window-to-floor ratio, the greater the wind speed, the smaller the air age, the greater the air change rate and the smaller the non-uniformity coefficient, the better the indoor ventilation effect. When the windward (south) courtyard is set, the air age is small, the air change rate is large and the wind field distribution is relatively uniform, which is the optimal scheme for natural ventilation. It is suggested that the relevant standards should set more targeted evluation indexes for the ventilation effect of underground space.