As a branch of rail transit system, the sky train has a research and application history of more than 100 years, which is mainly used in flat areas. In order to expand the applicable scope of the sky train, and reduce route length, optimization design and construction cost, the sky train is combined with tunnel in mountainous areas. And then the advantages and disadvantages of several structure forms in tunnel are qualitatively compared and analyzed from the aspects of structural stress, structural materials, construction and operation maintenance. When adopting the form of beam and column structure in the tunnel, the tunnel and the beamcolumn structure are two relatively independent systems, which does not need special requirements for the tunnel lining structure, and is with clear stress condition and mature technology, thus the factory production and prefabricated construction can be carried out. It is suggested that the structure form of tunnel beam and column should be preferred.