Abstract: The theory and the devices of the pulsed wire magnetic measurement system are described. The effects on the measurement accuracy of wire gravity, noise and reflected signal are theoretically analyzed. Some methods such as symmetric wire mounting, night measuring and lownoise circuit design are proposed for optimizing various components of the device to reduce the effects. The results of magnetic measurement of the pulsed wire system are compared with that of Hall probe method. It is applied to measure the practical electromagnetic undulator to be put to use in National Synchrotron Radiation Laboratory and verify the current relationship between the correction coils and main coils．