In this paper we consider the biharmonic equation △^2u=λ|u|^q-2u/|x|^4+|u|^2^**-2u in a smooth bounded domain Ω属于R^N with boundary condition u|偏导Ω=偏导u/偏导v|偏导Ω=0,where N≥5,1<q<2,λ>0 and 2^**=2N/N-4. We prove the existence of λ^* such that for 0<λ<λ^* the above problem has a positive solution.