It is common to see the phenomenon of serious floor heave of gob-side entry retaining with large section in deep mine. To reveal the mechanism of floor heave of gob-side entry retaining with large section in deep mine; based on the engineering geological condition of 1115(1) working face tailentry and with the self-developed physical model test equipment, a study about the dynamic evolution law of floor fracture and floor fractal dimension in excavation period, the first mining influenced period, roadway retaining period, the second mining influenced period is conducted according to fractal geometry theory. And the relation between floor fractal dimension and floor heave is obtained. The results show that: First, the floor fracture developed, expanded and penetrated gradually with mining, and the fracture distributed mainly in middle and high angles because of shear failure. Second, the fractal dimension of floor fracture increased gradually, and there is a significant rise during main roof caving and roadway retaining. Third, as the spring back of main roof; the load from overlying strata of the second working face is small; the bottom fractal dimension increases slowly. Fourth, the relation between floor heave and fractal dimension is nonlinear and positive. By comparing the field measured and tested results of floor heave, it is found that the both two can be able to fit, so as to verify the model test results is reliable.