Inadequate participation of private capital has become a major constraint for the continuous promotion of the Public-Private Partnership (PPP) mode in urban rail transit projects in China. Identifying and analyzing the obstacles to private capital participation is the key issue in promoting PPP participation. Through literature research, a total of 23 obstacle factors from four angles are extracted, and a hierarchical structure model of obstacle factors for private capital participation is established by using the method of an explanatory structure model. The hierarchical relationship of obstacle factors is obtained, and suggestions for promoting participation are put forward. This study provides theoretical support for promoting private capital to participate in PPP projects of urban rail transit.