The invention belongs to the technical field of monocrystal growth, relates to an apparatus suitable for flux technology monocrystal growth, and especially relates to a flux technology growth apparatus and a method of rare earth doped orthophosphate crystals. The method comprises the following steps: mixing lead oxide with lead fluoride, compacting the lead oxide with lead fluoride to form a cylindrical block structure in order to obtain a flux, disposing a YbPO4 and YPO4 mixture in the bottom of an inner wall, compacting the mixture, and disposing the flux on the mixture; and screw-capping an upper cover on an outer wall, sealing the upper cover, disposing the growth apparatus in a heating furnace, adjusting the temperature of the heating furnace, heating to 800DEG C, and sequentially cooling to 750DEG C, 700DEG C, 600DEG C, 500DEG C and room temperature to end crystal growth. The apparatus adopted in the invention has the advantages of simple structure, convenient operation, low cost, less energy consumption, reduction of the energy loss due to reduction of the crystal growth temperature to 400DEG C, high dimensions and high quality of grown crystals, reduction of discharge of toxic substances, and environmental protection.