Abstract: In order to inspect the surface topography of spherical target accurately, efficiently and exhaustively, which is the core component in inertial confinement fusion experiment, a shape detection system is founded based on the technologies of sub-aperture stitching and diffraction interferometry. The basic testing principle and the calculation method of lateral resolution in once single measurement are provided. The configuration of sub-aperture is planned for the rotation scanning of the target. In order to solve the problem that the matching algorithm shows a slow convergence rate or even misconvergence caused by the overlarge lateral distance between cloud data points, a method of data points transverse compression is proposed, which replaces the actual radius of curvature by a virtual tiny radius. This method can improve the matching rate and the accuracy of the algorithm with the topography feature remaining unchanged. At last, a gold coated target with a diameter of 1mm is measured actually, and the PV value and RMS value of the relative topography errors after stitched are 1.332 and 0.479 respectively. The macroscopic fluctuation characteristics and the partial topography detail can be obtained, and the refactored target surface has a good visual quality.