Nowadays, military threats are becoming more important as a form of new tools. A review of public places with passive defense approach shows that the existence of underground places is essential for enforcing the military forces of country. Designing these places is roughly difficult because of their unique mental and psychological characteristics. These places need to a level of livability to maintain. The main goal of this article is to explore the important variables of livability in safe underground spaces. The research method in this article is based on survey analysis and uses deep interviews with professors and specialists at this domain. According to the grounded theory approach, an axis coding is done and the results are gathered by means of this technique. The findings of this paper show that professors have emphasized on five categories of visual-physical, perceptual, environmental, functional and social. Also, they indicated twenty one factors which are effective on livability of underground public spaces in Tehran. Finally, some solutions are recommended.