Abstract: Application the repeated measurement data of high-density resistivity method, the paper discusses the laws of formation resistivity change with tidal wave in north part coastal area of Weifang city.The results showed that, in homogeneous ground, formation resistivity value has significant difference only in vertical direction under both single and repeated measurement.Formation resistivity is obviously affected by tides in coastal area.Chang e in formation resistivity near the water table is most obvious with the tidal, so using continuous repeated measurements data of high density resistivity method to analysis the changes of formation resistivity with tidal wave in coastal area is feasible.