Abstract: The aim of this paper is to investigate the second-order harmonic field characteristics of the solid-solid interface under P wave incidence according to the second-order potential theory.We consider an isotropic solid-solid interface and solve the boundary value problem of the second-order potential non-homogeneous equation based on the parameter variation method.The numerical computation is performed to analyze the relationship between the incident angle and the second-order harmonic displacement by modifying the incident angle.The results show that when the incident angle approaches a certain angle,the displacement of the second-order harmonic field will increase steeply.Moreover,the displacement mutation of the non-homogeneous solution still arises when the incident angle reaches atθ_w.Finally,the effect of boundary surface on the second-order harmonic sound field is also discussed.