The intrusion phenomena in the system of two liquids which consists of hot solution (left layer) and cold water (right layer) was numerically studied at the Prandtl number Pr=6, the Lewis number Le=100, the Rayleigh number Ra=10⁶ to 10⁸ and the buoyancy ratio N=0.8 to 1.2. A finite difference method was employed for the numerical analyses of this two-layer convection. At buoyancy ratio N<1, thermal convection occurred first and salt-fingers with time. At N=1, interleaving phenomenon occurred with cylindrical Benard type roll cells. At N>1, solutal convection occurred and a stable two layer with a horizontal interface was formed with the lapse of time.