By taking the pile penetration as the expansion of a cylindrical cavity under the undrained condition and assuming small strain deformation in the elastic region and large strain deformation in the plastic region, the lateral displacement of ground due to a single pile installation is derived in modified Cam clay critical state soil. Meanwhile, the difference between the traditional overconsolidation ratio and the isotropic overconsolidation ratio is taken into account. Comparison between the predicted and the measured values from literature verifies the validity of the present solution. Furthermore, the proposed solution is developed to estimate the lateral displacements due to a single row of piles based on the assumption that superposition is applicable to the displacements. The effects of the number of piles, space of two adjacent piles, prebored hole and the overconsolidation ratio (OCR) on the calculation of displacements are conducted. The results show that the value of the displacement increase with the increasing piles number, and decreases with the increasing space of two adjacent piles and radius of prebored hole. The increase of OCR also leads to increase of displacement, however, that is not pronounced.