Based on the analysis of detection theory of two booms electric field instrument,the detailed design of the electric field instrument boarded on sounding rocket which is used in Meridian Project is presented.In order to reduce asymmetries and inconsistencies of the probe,aluminous spherical probe is adopted.The graphite coating is chosen to reduce the surface non-uniformity,and the particular shape design is used to eliminate the shadow effect of the boom.In order to improve the system dynamic range,four frequency ranges is selected,providing a set of analog signals subsequently directed to the data digitization and processing unit.Finally,several error considerations and the test results of system performance are presented.The bandwidth of this electric field instrument is 0～5MHz.The DC detection range is 0.1mV/m～±1V/m and the AC detection range is 10μV/m～50mV/m.The two-dimensional spatial electric field with intensity of 0～±1V/m can be measured.