Abstract: This paper presents a method of double-probe electric field in-orbit detection. Differences of three kinds of instrument including double-probe type, antenna type and electron drift type are briefly introduced. The principle，architecture and calibration method of double-probe spaceborne electric field sensor are described in detail. Sensitive probe and signal acquisition processing units are implemented and tested with sensor in-orbit environment simulation through resistive coupling. Experiment results indicate that noise amplitude spectrum intensity of band SLF,VLF,HF are less than 4 Vm-1Hz-1/2,1 Vm-1 Hz-1/2, 0.5 Vm-1Hz-1/2 separately.