The regularities of the solid solutions between the scheelite-type compounds and rare earth molybdates or tungstates were investigated by the atomic parameter-support vector machine method and the intelligent database of phase diagrams of molten salt systems. The crystal structure of scheelite-type compounds having M~IM′~Ⅲ(XO_4)_2 (X=Mo, W) as common formula and the formability of the continuous solid solution between these compounds and rare earth molybdates or tungstates were also investigated. Besides, the cell constants of these compounds can be calculated by some semi-empirical equations. Based on the obtained relationships, the results of computerized prediction of the solid solubility of TlPr(MoO_4)_2-Pr_2(MoO_4)_3 system have good agreement with experimental results. The regularities of the solid solutions between the scheelite-type compounds and rare earth molybdates or tungstates were investigated by the atomic parameter-support vector machine method and the intelligent database of phase diagrams of molten salt systems. The crystal structure of scheelite-type compounds having M ~ IM ’~ III (XO_4) _2 (X = Mo, W) as common formula and the formability of the continuous solid solution between these compounds and rare earth molybdates or tungstates were also investigated. Besides, the cell constants of these compounds can Based on the obtained relationships, the results of computerized prediction of the solid solubility of TlPr (MoO 4) 2-Pr 2 (MoO 4) 3 system have good agreement with experimental results.