Changsha is a typical zone hot in summer and cold in winter. By using the method of experiment, natural and mechanical ventilation's flow fields and temperature fields of a VDSF, which has been built in Changsha, its features were analyzed and compared. When the glazing spacing of glass curtain was 0.10 m,0.20 m,0.30 m and 0.40 m, natural ventilation could all be realized, and the effect of the latter two's natural and mechanical ventilation was very close. Also, the positions of the blind in the heat passage were studied, and the results showed that, when the glazing spacing was 0.40 m and the blind was located in the middle position or at a distance of 0.10 m from the external wall, the effect of natural ventilation and mechanical ventilation was basically identical. In order to find out the natural ventilation's optimum glazing spacing and the best position of the blind in summer, this paper has simulated four conditions with Fluent respectively, the glazing spacing was 0.30 m and 0.40 m, and the blind was located in the middle position at a distance of 0.10 m from the external wall. The results showed that, in summer, the natural ventilation's optimum glazing spacing is 0.30 m, and the blind from the outer glass is 0.10 m.