Under the condition of normal gravity, it is difficult to perceive weak changes of microscopic matter caused by material combustion. To meet the requirement of long-Term microgravity environment, it is necessary to establish a combustion science experimental system in space station. For combustion experiment on orbit, a compact optical observation facility is designed in this paper. The facility bases on schlieren imaging, which is able to observe density distribution and flow-field change in combustion experiment. According to the characteristics of space condition, a highly reliable optical lens and mechanical structure are designed. The simulation experimental results show that our design is of high reliability, which is able to be used in complex condition of space combustion experiment. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.