The formula to calculate the impact factor of binding interface (λ) was proposed and derived based on the composite of steel body and Babbitt layer. ZChSnSb11-6/20 steel composites with or without tin layer were prepared by arc spraying technology. And the mechanical properties were investigated. Then the mathematical relationship between the impact factor of binding interface (λ) and proportion of Babbitt (ξ) was obtained. Results revealed that the impact factor of binding interface of composites without tinning (λ1) decreased monotonically with the proportion of Babbitt (ξ). However, for the composites with tinning, the function of λ2 and ξ exits an inflection point which is ξ=0.597. This inflection point suggested that there was an optimal thickness of Babbitt layer, and the best binding between 20 steel and Babbitt layer was obtained. It was validated that the process of tin layer enhanced the interfacial binding properties of composites, and the binding force of interface was maximum when ξ was 0.6.