For measuring the explosive radiation electromagnetic pulse (EMP) with fast rise time, narrow pulse width and intense field strength, an integrated optical waveguide electric field sensor is designed and developed. The sensor detected waveform of the applied lightning EMP in the time domain shows almost without distortion in comparison with the original voltage waveform. The minimum and maximum measurable electric fields in time domain are 1. 4 and 10. 8 kV/ m, and the minimum measurable electric fields in the frequency domain is 52. 5 mV/ m. The response fluctuation is within ±4 dB in the frequency range of 9 kHz to 1 GHz. Finally, the insitu testing system of explosive EMP has been setup based on the developed optical waveguide electric field sensor. The radiation EMP at different distance from the explosion place has been measured in the time domain. Results show that the radiation EMP is generated after the explosion for about several milliseconds. The radiation EMP is a series of bipolar pulse train, the width of a single pulse is less than 100 μs, the width of the pulse train is less than 2 ms, and the frequency range is 17. 5 ~ 35 kHz. The EMP field intensity within 5 m from the explosive is about 5 ~ 10 kV/ m. The developed sensor has characteristics of full passive, wide bandwidth, negligible field interference, small volume, and good electromagnetic immunity, which provides a new technique for measurement of the explosive radiation EMP.