Abstract: The distinguishing of connectivity of structural planes is an applicative problem in rock mass engineering because of the lack of the relevant theoretical basis. So, it has an important theoretical meaning that the connectivity principle and distinguishing method of the structural planes is studied. Firstly, the coplanarity conditions of any two structural planes in engineering rock mass space are analyzed by using the mathematical methods such as space geometry and vector. Secondly, the similarity conditions between any two structural planes are demonstrated on the basis of the geological features. Thirdly, the distinguishing conditions of connection of the structural planes are given, and formulas for the correlativity of the structural planes are put forward. So, a complete set of theoretical system of the connectivity principle and the distinguishing method of the structural planes is established. Finally, combining the survey data of Zn-polymetallic ore body in the roadway of Tongkeng Mine in Guangxi Province, the application effect of the above theory is studied. The results show the connectivity of the structural planes can be judged quickly and effectively using the proposed principle and method. This study may provide a theory basis for judging the connectivity of the structural planes in other rock mass projects.