Based on the separation data collected from a comprehensive underground monitoring in a coal mine, this paper presents an analytical work on the characteristics of roof separation propagation and process under the high horizontal stress condition in the longwall roadway. The work is focused on the roof separation propagation characteristics, associated with different mining activities, including stages of heading development and longwall extraction. It is found that roof separation is strongly related to different stages of mining activities, and each stage involves different separation characteristics and mechanisms. Major separation occurs almost uniformly with formation of opening from the roof surface up to 6m。 Then two separation zones are formed in both lower and upper roof strata respectively。Furthermore, two separation zones emerge gradually，and the separation zone covers from roof surface up to 6m，which is two times of the heading height. During formation of opening, the separation characteristics of roof strata are dominated by the maximum roof separation and afterwards, the density of separation plays an important role.