In the context, a novel composite synthesis technology is engaged in the preparation of NaRE(MoO4)(2) (RE=Y, La, Nd, Eu, Gd, Tb, Er, and Yb) and Na5Lu(MoO4)(4) compounds, which involves a room-temperature solid-state reaction and hydrothermal crystallization process. The synthesis mechanism is predicted, indicating that higher temperature and moisture can speed up the reaction process and especially the existence of crystalline water molecules in the precursor is necessary for the solid-state reaction at room temperature. It is found that different rare-earth nitrate precursors present different reactivity to sodium molybdate at room temperature. The crystallization degree of the products after the room-temperature solid-state reaction depends on the melting point of rare-earth nitrate precursors. The hydrothermal treatment is beneficial for the good crystallization of NaRE(MoO4)(2) (RE=Y, La, Nd, Eu, Gd, Tb, Er, and Yb) and Na5Lu(MoO4)(4). Finally, the photoluminescent spectra for these NaRE(MoO4)(2):Eu3+ (La, Gd, and Y) are studied, which depend on the species of rare-earth ions.