This paper studied the fractal characteristic of the interfacial shear surface of steel-Al solid to liquid bonding plate, and determined the relationship between fractal dimension and interfacial shear strength. The research results showed that the relationship between fractal dimension and interfacial shear strength could be described as y=26.2x+4.2 (where y was intedecial shear strength, x was fractal dimension) and when O8Al steel plate was coarsened by steel wire wheel which was made up with steel wires whose diameter were 1.4~1.6 mm, the optimum coarsening pattern of the steel plate sudece could be got, the corresponding maximum interfacial shear surface fractal dimension of the bonding plate was 2.33, and the maximum intedecial shear strength of the bonding plate was 65.3 MPa This paper studied the fractal characteristic of the interfacial shear surface of steel-Al solid to liquid bonding plate, and determined the relationship between fractal dimension and interfacial shear strength. The research results showed that the relationship between fractal dimension and interfacial shear strength could be described as y = 26.2x + 4.2 (where y was intedecial shear strength, x was fractal dimension) and when O8Al steel plate was coarsened by steel wire wheel which was made up with steel wires whose diameter were 1.4-1.6 mm, the optimum coarsening pattern of the steel plate sudece could be got, the corresponding maximum interfacial shear surface fractal dimension of the bonding plate was 2.33, and the maximum intedecial shear strength of the bonding plate was 65.3 MPa