A wavefront reconstruction error analysis method based on the phase diversity (PD) method for diffraction optical systems is proposed. Based on the wavefront reconstruction model of the diffraction optical system, the physical factors which cause wavefront reconstruction error are analyzed, and the influencing factors are theoretically modeled. Furthermore, the analysis method for wavefront reconstruction error is established. Taking a diffraction optical system as an application example, the influences of various physical factors on the wavefront reconstruction error are analyzed, and the error analysis model and method are verified. The experimental results show that the average deviation between the wavefront reconstruction error obtained by the error analysis model and the actual error is less than 13.5%. The method proposed in this paper can be used as the basis of application of space based diffraction optical systems.