Large-scale oil wharves usually adopt the layout of butterfly.Generally,the critical loading relating to the overall structure stability is the wave loading.Typically,the maximum wave height and its corresponding wave period or the maximum wave period and its corresponding wave height are chosen are the design wave parameters.However,it is indicated by calculations that those are not necessarily the critical condition regarding the wave parameters.By reference to the numerical analysis result of the factor of pile group,this paper studies the change of wave loading on small-scale pier column structure with different wave heights and wave periods,and also studies the general pattern of the overall stability of separate caisson dolphin structures.