The bandgap characteristics of two-dimensional phononic crystals in a triangular lattice with imperfect interface conditions were studied by using the boundary element method. Combined with Bloch theorem, the boundary element eigenvalue equations with imperfect interface conditions were derived for the two-component solid-solid phononic crystal in a triangular lattice. Based on the equation, the band structures of phononic crystals with different cross-section scatterers (circular, elliptical and square cross-section) were calculated, and the effects of the lattice symmetry on the band structures were discussed; additionally, the influences of the scatterer filling ratio on the position and width of the bandgaps were analyzed in the case of circular cross-section. Compared with other results calculated by other methods, it is shown that the boundary element method can effectively and accurately calculate the band structures of phononic crystals with different interface conditions and different shaped scatterers. Moreover, phononic crystals with imperfect interface conditions can open the complete band gap at low frequencies, especially for the phononic crystals with the circular cross-section.