in this paper, a colorful schlieren system without any protecting windows was introduced which results in that the 1.2m primary mirror would directly be confronted with the pressure and temperature variation from the wind tunnel test. to achieve a good schlieren image under the wind tunnel test working condition of a wide temperature fluctuation range (-10°c to 50°c) as well as a pressure (2kpa), a new flexible support method of the primary mirror was strategically designed. a finite element model of the primary mirror combined with its supporting structures was built up to approach the surface figure of the primary mirror under the complex working conditions as gravity, temperature variation, and pressure. the schlieren images due to the change of the primary mirror surface figure were simulated by light-tools software. it was found that the temperature changing and pressure would lead to the variation of the surface figure of the primary mirror surface figure and therefore, results in the changing of the quality of simulated schlieren images. © 2017 spie.