In the theory of pile vibration, one-dimensional assumption is not suitable for the large diameter pile. The influence of lateral inertial effect must be taken into account. This paper presents the solution of the motion equation of lateral inertial effect with Laplace transforms and develops the velocity response function under semi-sine wave exciting force at the level of pile tip. The paper also presents the analysis on the influence of lateral inertial effect of the dynamic response curves in the time-domain and its factors. Taking no account of the influence of pile material damping and the surrounding soil, it is found that both the velocity decreasing and attenuation of the stress wave are due to the lateral inertial effect. Meanwhile，different pulses and diameters also have an important influence on the lateral inertial effect.