This paper studied the bubble coalescence in ship wake based on LES and the developed bubble population balance equation (D-BPBE) by us. the results indicate that coalescence make less affect to the distribution of bubble number density (BND) but main effect to the volume fraction of the vapor, the reason is that coalescence took place much more when there is large bubble included, though the BND ratio of large bubble is much small compared to the whole BND, but it is the main carrier of the vapor, so decides the distribution of the volume fraction of the vapor with the flow direction straightly. What’s more, in the near field of the wake(less than 1.8km), the volume fraction of the vapor almost attenuates to the power law, and in the far field of the wake the volume fraction of the vapor attenuates to the linear law. The conclusions of this paper make up the important study shortage that the function of the bubble coalescence in the wake can’t be assured all long.