In　[F.　Jiang　and　S.　Jiang,　Adv.　Math.,　264,　831-863,　2014],　the　author　and　Jiang　investigated　the　instability　of　Rayleigh　Taylor　steady-state　of　a　three-dimensional　nonhomogeneous　incompressible　viscous　flow　driven　by　gravity　in　a　bounded　domain　Omega　of　class　C-2.　In　particular,　we　proved　the　steady-state　is　nonlinearly　unstable　under　a　restrictive　condition　of　that　the　derivative　function　of　steady　density　possesses　a　positive　lower　bound.　In　this　article,　by　exploiting　a　standard　energy　functional　and　more-refined　analysis　of　error　estimates　in　the　bootstrap　argument,　we　further　show　the　nonlinear　instability　result　without　the　restrictive　condition.