Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China
; Grad Univ, Chinese Acad Sci, Beijing 100049, Peoples R China
An improved kinematic fit method is developed for analyzing all-photon events, where the interaction point is unknown. The fitting algorithm is checked with Monte Carlo samples to ensure that the fitting program works properly. This is applied to the Monte Carlo simulated psi(2S) decays. A higher efficiency is achieved. This method can be generally applied to analyzing all-photon events at electron-positron collider.