Evaluation of coal roadway bolt-mesh-anchor supporting effect and the main means of roadway safety were the roof separation instrument, this paper introduced the working principle, roof separation meter reading method, installation method, basic fixed position, requirements of installation space and the special place of the installed in the construction of tunnel. And the roof separation indicator data observation, data analysis, data processing and taken to the roof separation data exceeding the critical value measures were discussed, which had the certain instruction significance to support the roof separation monitoring of anchor cable in roadway.