Abstract: It takes some time to form the phenomenon of zonal disintegration of surrounding rocks with high in situ stress,but the time needed is not too long.The creep theory is used to analyze the time effect of zonal disintegration of rocks and deduce the constitutive equation and creep equation of the improved Nishibara rheological model which can describe the third(accelerated) creep stage.On that basis,we can find the fracture zone radius(the distance from the fracture zone to the center of a tunnel) formula during the zonal disintegration of rocks.