This paper introduces a design of different-frequency grounding resistance meter using MCU 80C196KB as the core. This instrument generates a current with a different frequency at about 120Hz to be injected into the ground grid. By adopting current-voltage method, the design enables an accurate measurement of the grounding resistance of large-scale ground grid, such as, power systems, architectural buildings, military facilities, and airports. The instrument controls the output of different-frequency electrical source by using MCU and DDS techniques. Moreover, the utilization of RMS-DC devices simplifies its data acquisition and data processing. In addition, the application of hardware and software filtering technology reduces the measurement error which may be caused by frequency interference, measuring disturbing between lead wires.