The measured fields of the optical klystron in NSRL (National Sychrotron Radiation Laboratory) are given, including the distribution on the axis, and the integrated field distribution. The harmonic magnet field and the spectra of the spontaneous emission are analyzed, and the multiple field is presented by fitting the diagram. The influence of the integrated field on the close orbit of the beam and on the operation parameters of the storage ring, and the compensation in the experiment are also discussed.