Most of the underground coal gasification (UCG) field tests worldwide were carried out in shallow coal seams, but were heavily restricted by environmental concerns. The environmental protection advantages of medium–deep UCG projects are outstanding and the development prospect is better than that of shallow coal seams. However, site selection factors are more complex and underground engineering is much more difficult. In this regard, we first investigated the development status of UCG technologies at home and abroad, then summarized the main issues faced by UCG technology commercialization, and discussed how to achieve the commercialization of medium–deep UCG projects. Comparatively with shallow coal seam gasification having a great environmental risk, medium–deep UCG projects are relatively more difficult especially in engineering. Under the current technical level, the economy of UCG project investment is poor and site selection and system matching have a great impact on the competitiveness of UCG projects. From the perspective of investment economy, the underground gasification unit (UGU) in medium–deep UCG projects requires the design not only with high daily and cumulative syngas production rates and rather long gasification channels to control a lot of coal resources, but with solutions to such problems like blockage and failure of such gasification channels. Site selection of medium–deep UCG projects, intensive of fund and technology, will fully consider underground conditions, product market and supporting conditions of public engineering system, etc. In conclusion, China should give priority to such oil–gas production provinces with superior coal resources as eastern Junggar (Xinjiang), Hami, Santanghu, Ordos (Inner Mongolia), Erlian, Hailar, and so on, where UCG test bases can be constructed with deployment pilot tests and commercial projects. In this way, synergies will be achieved with the oil and gas industry chain and that will be one of the best paths to promote UCG technology research field tests and commercialization.