Abstract: This paper expatiates on the methods marginal, horizontal and vertical shimming magnet block of OK radiator in Hefi storage ring. By means of shimming,the filed integral and phase error can be reduced as much as possible. All the measurement results of magnetic field of optical klystron before and after shimming are given, including the distribution of field integral and phase error on axis, field integral and RMS phase error for different gaps and transverse distribution of field integral. The results reveal that the radiator can meet the requirement of coherent harmonic generation FEL experimental. The same method will be used in the shimming and measurement of modulator and dispersion section of optical klystron．