Abstract: This article described the synthesis methods and ion exchange behaviour of crystalline melamine-phosphomolybdic vanadate(MPMV). Extensive studies of this material have been carried out by X-ray, TG-DTA, IR and chemical analysis. Based on these analyses, the molecular composition and the parameter of unit cell of MPMV were determinated. Some ion exchange characteristics of the MPMV can be explained by these results. This material shows cation exchange behaviour with high ion exchange capacity of 0. 42 mmol/g for Cs from simulated solution.