Abstract: The researches on the mechanical property of rock structure plane has always been a hot topic.In order to study the mechanical property of rock mass at pre-and-post grouting, a FLAC3D calculation model is constructed based on ANSYS to perform calculation. The mechanical properties of three structural planes and two aspect ratio types are analyzed with aspect ratio are 0.5 and 0.3.The results show that the different step- shaped aspect ratios have the different failure laws, which exhibited shear failure with large aspect ratios and pressure -shear failure with small aspect ratios, and the shearing strength increased markedly after grouting. The concept of uncontrolled climbing angle is put forward according to the results.