In the underground roadway engineering, owing to rheological properties of rock mass that have brought difficulty on surrounding rock control of roadway, among anchorage surrounding rock mass, bolting long-term effective pretension is one of the key factors related to keep stable or not in service period of roadway. In allusion to roadway excavation, long term creep of rock mass lead to failure of bolting system, moreover affecting instability or failure of roadway, based on provisions that the change value of pretension should not exceed 10% than the design axial tension value of bolting, firstly to derive the relationship that bolt axial force of small element of Poyting-Thomson rheological model along with time by using rheological theory, and then to carry on calculation and analysis of bolting bearing reliability in specific bolting support structure of roadway. Results show that, in the service period of roadway, pretention continuous decrease along with time, and decrease speed to slow down, and finally tend to be stable, pretension change value in the allowed range 10%, therefore, bolting support parameters of roadway can be considered to be reliable, the roadway can be safe and reliable in its service period, and the research work has a certain theoretical and practical significance to guide bolting support design of coal roadway.