A novel member of the Prussian blue family, Cu3Ⅱ [FeⅢ (CN)6]2@ 3NH3@6H2O, was synthesized, in which NH3 ligands are in stochastic distribution. We present x-ray diffraction data, zero-field-cooled magnetization and fieldcooled magnetization curves, Mossbauer spectra with/without an exteal field of 5 T and a structural model. This Prussian blue analogue displays considerable magnetic hardness below the magnetic transition temperature Tc, which is about 19.8 K. The coercive field determined from the magnetization hysteresis loop at 5 K was 2. 76 kOe. The copper-iron cyanometallates have potential applications in the design of novel magnetic systems.