A new spin-cluster compound K6BaCo9(PO4H)3(PO4)6Cl2 was synthesized by the traditional solid-phase method. The fundamental magnetic unit of the compound is a coupled [Co9] cluster, which is composed of three non-coplanar triangles. These [Co9] clusters are interconnected by phosphate groups, constructing a two-dimensional framework in the ab plane. The crystal shows the clear easy-axis anisotropy. No long-range magnetic ordering was observed down to 2 K, but there is short-range spin correlation below T = 2.45 K. The Curie-Weiss temperature is about θCW = −19.38 K for the powder sample, which indicates that the dominant exchange interaction is antiferromagnetic with strong frustration (f = |θCW|/T ≈ 10). The magnetization curve presents a likely magnetic field induced transition at μ0Hc = 1.85 T.