The structures of single wall BC3 nanotubes are described in the present paper. The symmetry and lattice dynamics of single wall BC3 nanotubes are analyzed in detail. Based on the force constant model we calculate the phonon dispersion relations of single wall BC3 nanotubes with different diameters and chiralities. For Raman and infrared active modes, the diameter-dependence of vibrational frequency has been established. It can be inferred that the Raman and infrared spectra of BC3 nanotubes would be more complex than those of single carbon nanotubes.