Abstract: In the development of the near space and deep space exploration in China, the deficiency of the low density aerodynamic test facility has restricted the development and utilization of the related techniques. So it is highly desirable to build a subsonic low density wind tunnel. The design features, key technologies and test capabilities of several representative foreign subsonic low density wind tunnels are reviewed. It is shown that we have to face the low density and low Reynolds number aerodynamic issues due to the development of the aerospace integration and the deep space exploration. So China has to develop subsonic low density wind tunnels. The development direction and technology requirements of the subsonic low density wind tunnel in China are discussed through comparing several representative foreign subsonic low density wind tunnels.