A typical residential housing in Chongqing is taken as an example, which is with worse natural climate conditions and absent of wind resource. A feasibility study on improving the thermal environment by natural ventilation is analyzed based on the id chart. By the onsite tests，the indoor thermal comfort is evaluated based on the PMVPPD methodology. Better natural ventilation can not only save the building energy consumption, but also improve indoor thermal environment, especially in the rain and transition seasons, even in the urban area with poor wind resource.