The　title　compound　K-3[HO{VO(O-2)(2)}2](H2O)-H-.　has　been　synthesized　and　its　crystal　structure　was　determined　by　X-ray　diffraction　method.　The　crystal　is　of　monoclinic,　space　group　P2(1)/c　with　a　=　6.7078(3),　b　=　9.9539(6),　c　=　15.8182(9)　Angstrom,　beta　=　93.702(3)degrees,　V　=　1053.96(10)　Angstrom(3),　M-r　=　414.20,　D-c　=　2.610　g/cm(3),　Z　=　4,　lambda(MoKalpha)　=　0.71073　Angstrom,　F(000)　=　808,　mu　=　3.014　mm(-1),　the　final　R　=　0.0173　and　wR　=　0.0466　for　21.78　observed　reflections　with　I　＞　2sigma(I).　X-ray　diffraction　reveals　that　the　coordination　polyhedra　of　V　atoms　are　not　chemically　equivalent:　the　V(1)　and　V(2)　polyhedra　can　be　described　as　pentagonal　pyramid　and　pentagonal　bipyramid,　respectively.