Abstract: A small passive electro optic EMP sensor over frequency range from 10kHz to 700MHz has been developed. The sensor's operation properties,such as the frequency response, li near dynamic range, sensitivity, optical power dependence, dipole element length dependence and impulse response ，were measured, which agreed with the calculated results. It has the characteristics of wideband, passive, small size and being free from electromagnetic interference, and can be used for EMP measurement in small volum e．