The single photon frequency conversion is investigated theoretically in the system composed of a V-type system chiral coupling to a pair of waveguides.The single photon scattering amplitudes are obtained using the real-space Hamiltonian.The calculated results show that the probability of single photon frequency down-or up-conversion can reach a unit by choosing appropriate parameters in the non-dissipative system with perfect chiral coupling.We present a nonreciprocal single photon beam splitter whose frequency of the output photon is different from that of the input photon.The influences of dissipations and non-perfect chiral coupling on the single frequency conversion are also shown.Our results may be useful in designing quantum devices at the single-photon level.