The astrophysical S-factor for α-3H radiative capture is calculated at astrophysical energies.We construct conserved two-and three-body electromagnetic currents,using minimal substitution in the explicit momentum dependence of the two-and three-nucleon interactions.The realistic Argonne v18 two-nucleon and Urbana IX or Tucson-Melboue three-nucleon interactions are considered for calculation.By extrapolation of results for the astrophysical S-factor at zero energy,the energy in the order of 1 keV and less is found to be S(0) =0.107(0.112) keV.b,with(without) three-body interactions in satisfactory agreement with other theoretical results and experimental data.