A wideband, minitype and analog optical fiber system was designed for measuring instantaneous electric field produced by nuclear burst with a strong electromagnetic interference. In the system, a monopole antenna was used to convert electric field into voltage, at the same time a minitype transmitter converted voltage into optical signal, and the optical signal was send to the receiver which was far away from transmitter by the optical fiber, finally the voltage was received at the receiver. The system was of good performance, with bandwidth 24 kHz~1 000 MHz, noise smaller than 12 mV.