On the basis of the electric field distribution characteristics produced by underground-orientated current supply from singlepoint electrode (or multi-point electrode) and infinite electrode and through detection of potential difference distribution at surface, we can determine the buried depth of underground single-point electrode (or multi-point electrode) and, on such a basis, determine the length of the concrete pipe pile. In combination with the inspection of the real pile length of the prestress pipe pile, the authors made electric logging comparative test and found that the inspection was successful. The achievements made by the authors can remedy the ineffectiveness of the low strain reflection wave method and overcome the difficulty in precise determination of the practical length of the multi-joint prestress pipe pile. It is thus held that geophysical electric method can be used to determine the length of the engineering pile and prevent the hidden trouble in engineering quality caused by saving illegally on material and labor.