Abstract: 3D reconstruction of targets in Interferometric SAR (InSAR) refers to determine targets 3D position based on principal measurements of radar and the InSAR imaging geom-etry. Several algorithms have boon proposed for InSAR. These algorithms rely on simplifying assumptions, such as the; flat oarth approximation and the plane wave approximation. Signifi-cant location errors of targets have been introduced by these approximations. In this paper, a new algorithm is proposed on the models of spherical earth and spherical wave. The solution is given in a closed form only using the measured quantities: orbit, parameters, range time, Doppler shift, and interferomotric phase. This analytical solution demonstrates more exact than the existing algorithms.