Abstract: Within a distance of about 250 km from the epicenter of the 1976 Tangshan Earthquake, 16 earth resistivity stations had been established. About 10 days before the occurrence of the earthquake, certain stations recorded sudden variations of large amplitudes of earth resistivity values on a rather quiet background, despite such stations are rather few in number.According to the result of focal mechanism solution of the Tangshan earthquake and earthquake fault investigation as well as data from groundwater level changes, it can be seen that the places with sudden earth resistivity variations are located along the earthquake fault and also on a belt of groundwater level changes which in time are at the same pace with the changes of earth resistivity.