In the method of iterative shift-and-add for astronomical image reconstruction, a key problem is to determine whether the developing direction and the convergence result of the iterative process are correct. According to the properties that an object bispectrum corrsponds to the image of the object in speckle masking method, the object bispectrum is adopted as the standard function to test the iterative results. The method of least-square is used to distinguish the developing direction and convergence result of the iterative process, so that the blind action of the iterative process can be avoided and a correct reconstructed image will be got.