The calibration of measuring network in medical leakage current testers is researched in compliance with the standard of GB 9706.1-2007. It is necessary to calibrate the input-impedance and transfer-characteristic in the frequency range from DC to 1MHz. It is pointed out that correct frequency response characters are the precondition of leakage current measurement, and the calibration method of network is proposed, whose standard values of input-impedance and transfer-ratio are calculated then. The influence of distributed inductance on the calibration of transfer-characteristic is analyzed, and the high frequency common-mode-rejection ability of voltage meter in network’s respond port is the main error source. Based on the technologies of DDS, I-V conversion and isolation-measurement, a multifunctional leakage current calibrator is developed, which can take automatic sweep in frequency to calibrations of input-impedance and transfer-ratio. The Calibrator meets the requirements of medical leakage current testers well.