The interface behavior of multiple piezoelectric films attaching to a gradient substrate under the action of electromechanical coupling is studied. The effect of neighboring films on the interface response is mainly concerned, including the interface stress, the stress intensity factors near both ends of piezoelectric films and the normal stress of films. In order to solve such a boundary value problem, Fourier transformation is used to achieve governing integro-differential equations, which could further demonstrate the interface behavior. The results show that, in comparison with the single-film model, both the interface stress and the normal stress of films are significantly affected by adjacent piezoelectric films. When the equivalent stiffness of the substrate or the distance between neighboring piezoelectric films becomes larger, the interaction between adjacent piezoelectric films gradually weakens. In addition, both shorter piezoelectric films and softer or thicker intermediate adhesive layers are beneficial to the interface property. The results should be helpful for the accurate measurement of surface sensors and the arrangement of multipoint health detection of gradient structures.