Based on the related psychological and physiological advancement, a just noticeable disparity difference (JNDiD) model for 3D displays under the assumption that eyes converge at the virtual object is presented in this paper. Specifically, according to whether the surface of the virtual object is perceived to be blurred, the perceived depth space is divided into three regions. Furthermore, a three-phase linear function considering the accommodation convergence mismatch in different depth regions is employed to build the JNDiD model. Experimental results demonstrate the effectiveness and superiority of our method compared with the state-of-the-art just noticeable depth difference (JNDD) model for 3D displays.