First-principle calculations were performed to study the adsorption of boron and its relationship with the morphologies of TiC. It is found that although the adsorption of boron on all the low-index TiC crystal planes is thermally favorable, it will be adsorbed more easily by C-terminated {111} and {011} planes, while less possible to be adsorbed by {001}. The study of the formation of B-B clusters indicates that the distribution of boron adatoms on C-terminated (111) and {011} planes will be more uniform, and the diffusion of the adatom further confirms the above results. According to the geometry relationship and growth rate of different crystal planes, it is deduced that the adsorption of boron on TiC will seriously impede the growth of {111} and {011} planes, which can make TiC grow into hexagonal platelets.