U:CaF2 crystals, which can be used as passive Q-switch at 1.54 μm, were successfully grown by TGT with uranyl nitrate, calcium fluoride and lead fluoride as raw materials. The distribution coefficient of uranium in CaF2 is equal to 0.53, which was calculated through determining concentrations of U in various parts of U:CaF2 single crystals by ICP-MS. Through changing the proportions of raw materials, uranium ions with various valences in CaF2 crystals were produced As-grown crystal without PbF2 is U4+:CaFa while the crystal grown in the presence of PbFz is U3+:CaF2, even U2+:CaF2 in the periphery near the graphite crucible. It is indicated that PbF2 could regulate the valences of uranium ions.