The tests were performed using various electrical resistivity tomography (ERT) electrode arrangements to discuss the variation of electrical resistivity of the ground at three different periods in Wan-ya, Zhanghua County. The results of ERT measurements are consistent with the drilling data; the changes of water in strata are also well estimated. In addition, the relationships between ERT measurements and SPT N-values are obtained by using an equation proposed in literature. Based on the equation, the resistivity obtained from ERT measurements is converted into transverse resistivity for correlating with the N-values. The results indicate that the characteristic of the strata in Wan-ya has an important influence on the correlation between transverse resistivity and N-value.