Abstract: In order to study the critical depth of roadway surrounding rock, we established a mechanical model which considered coupling effect based on elastic bending theory. "The coupling effect factor ξ" was introduced to characterize the effect of multi-factor coupling including groundwater, temperature and geological structure. Thus, "the critical depth equation" was established. In addition, the mechanical mechanism of surrounding rock instability was discussed in four aspects, which is structure, displacement, stability and stress state. Finally, we used an engineering example as an example of the model, conclusion are drawn that the critical depth under the present conditions is 960.0 m, and roadway's critical depth increased 510.2 m by the effect of multi-factor coupling.