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Nb3Ga wires fabricated by using RHQ (rapidly heating and quenching) treatment show Tc = 29.7 K and Bc2 (4.2 K) = 32 T. In addition Jc of the Nb3Ga phase is very high, comparable to those of practical (Nb, Ti)3Sn wire and RHQT-processed Nb3Al wire. However we cannot obtain the large overall Jc for the wire, because of small volume fraction of Nb3Ga in the wire. By using Ta-matrix Nb3Ga precursor wire, we performed the RHQ treatment at higher temperatures, resulting in two-times improvement of overall Jc and a little improvement in Jc. We measured temperature dependence of Jc vs. B curve for the Nb3Ga wire. The pinning force vs. B curves did not show any agreement with Kramer's scaling law. TEM observations clarified that the composition of Nb3Ga varies from near-stoichiometry (24at%Ga) nearby the Nb5Ga3 phase to Ga-poor composition (21.8at%) nearby the Nb-Ga bcc phase. We also measured the tensile strain effect on the superconducting properties of Nb3Ga wire. The strain effect of Nb3Ga wire is as large as that of Nb3Sn wire.