A mixed-valence polyoxovanadate(DienH3)2(DienH2)[(VⅣ8VⅤ10)O42(PO4)](PO4)·H2O has been hydrothermally synthesized and characterized by elemental analysis,TAG,IR, ESR and X-ray diffraction.Crystal data:monoclinic, space group C2/c,a=23.728(4),b=12.998(2) ,c=20.089(4) ,β=106.072(3)°,V=5953.4(18)3,Z=4,Dc=2.516g/cm3,C12H52N9O51P2V18,Mr=2116.99,R=0.0974,wR=0.2107(Dien=diethylenetriamine).