Abstract: The main component of experiment equipment of coherent harmonic radiation in Hefei is optical klystron. To increase the electron beam energy for experiment, the symmetrical configuration of optical klystron is shifted to nonsymmetrical configuration. The total integral field of old optical klystron is small, but the magnetic gaps of the three sections are not adjusted solely. After reconstruction, the three sections must be adjusted solely, so the integral field of every one section must be much small. The magnetic field distribution of undulator of radiation section is shimmed and the integral field and optical phase error are decreased effectively after shimmed.