In order to study the surgeinduced transverse oscillations in port pools, the fully nonlinear Boussinesq numerical model FUNWAVE 2.0 is used to simulate the transverse oscillation of mode in a rectangular port pool with hyperbolic cosine water depth. It is found that only by setting a small transverse slope at the bottom of the port pool can the transverse oscillation be successfully excited, whereas no obvious transverse oscillation can be excited under the condition that the transverse water depth remains unchanged. By analyzing the effects of longitudinal slope, transverse slope and incident wave height on transverse oscillation, the influence of transverse slope is understood. When the amplitude of transverse oscillation is small, it keeps a linear relationship with the transverse amplitude; when the amplitude of transverse oscillation is large, it is limited by the nonlinear intensity and grows slowly; and when the longitudinal slope is large and the incident wave height is small, the amplitude of transverse oscillation can exceed the longitudinal oscillation and dominate the water movement in the harbor after growing for a certain period of time. All the transverse oscillations mentioned above are the results of nonlinear effect, rather than those simply caused by the diffraction that is caused by topographic changes.