In this paper，a new earthing system using reinforcing bars in house foundations was proposed. We are studying ability of earthing system for lightning protection in the case of setting the system in the detached houses. It was prepared some experimental models based on the reinforced concrete foundation for house. It was examined overvoltage suppression effect by the combined use of surge protective device and lightning impulse withstand current performance. We obtained the results on the overvoltage suppression effect in changing the area of pseudo earth on experimental models. It was estimated the overvoltage suppression effect of applying the earthing system in detached houses by EMTP analysis using the experimental data and an equivalent circuit of reinforced concret foundation. Thus，it was confirmed to be suppressed to below 0.3kV on overvoltage applied to electrical equipment. About lightning impulse withstand current performance，it was confirmed the experimental model had enough tolerant to flowing peak current of about 10kA. As a result，it can be said that the earthing system is expected as good earthing for lightning protection.
