In the light of the condition of large-depth complex rock top consisting of thin layers, the large ratio tri-dimensional similar simulation experiment of roadway has been carried out according to the theory of similar simulation. The experimental results have shown that with the working-face being advanced forward, the dynamic-load coefficient increased, cracks started to produce, extended and connected in surrounding rock of roadway, finally resulting in the breaking of roadway. Based on analyzing by the theory of fractal geometry, it is considered that the crack distributing density confirm with fractal character, can be used to quantitatively describe the distribution of cracks in the surrounding rock of roadway. The analyzed results offer the theory basis for selecting supporting scheme of roadway and optimizing design parameters of roadway support.