Homoclinic bifurcation is an important global bifurcation in the study of nonlinear dynamics.As we known, for an autonomous two-dimensional system with a homoclinic orbit to a saddle, ira perturbation term that is periodic with time is added, then the relationship between the stable and unstable manifolds near the saddle of the Poincare map for the system may have three cases: separation, transversal intersection and homoclinic tangency.