A planar Ge(Li) detector of active area 4.5 cm2, drifting depth 4 mm was completed and its fabricating procedure was described in detail. The energy resolution of the detector was measured to be 3.3 keV with the ORTEC 120-3F preamplifier, ORTEC 410 linear amplifier and detector bias of 500 volts. Its characteristic curves of the current-bias and the capacitance-bias were also measured.