The VUV-vis spectroscopic properties of Tb3+ activated fluoro-apatite phosphors Ca(6)Ln(2-x)Tb(x)Na(2)(PO4)(6)F-2(Ln = Gd, La) were studied. The results show that phosphors Ca6Gd2-xTbxNa2(PO4)(6)F-2 with Gd3+ ions as sensitizers have intense absorption in the VUV range. The emission color of both phosphors can be tuned from blue to green by changing the doping concentration of Tb3+ under 172 nm excitation. The visible quantum cutting (QC) via cross relaxation between Tb3+ ions was observed in cases with and without Gd3+. Though QC can be realized in phosphors Ca6La2-xTbxNa2(PO4)(6)F-2, we found that Gd3+-containg phosphors have a higher QC efficiency, confirming that the Gd3+ ion indeed plays an important role during the quantum cutting process. In addition, the energy transfer process from Gd3+ to Tb3+ as well as D-5(3)-D-5(4) cross relaxation was investigated and discussed in terms of luminescence spectra and decay curves.