Complex fluorides ARF(4) (A = Li, Na, K, R = rare earthes) are synthesized by the mechanochemical solid reactions of AF and RF3 powders at room temperature using a planetary ball mill. The reactions proceed with the increase of grinding time and have been completed at 4h. Transmission electron microscope observation shows that the produced ARF(4) powders consist of agglomerates of nano-sized primary particles, which exhibit moderate water solubility. When the ground sample is calcined, the particle size is increased and the water solubility is depressed.