Three-fluid dam-break experiments were conducted to observe the mixing and stratification processes of three immiscible fluids (two-liquids and one gas) by gravity. Two liquids (silicone oil and salt water) were separated with a vertical wall and filled in a rectangle container. Fluid motions are visualized by four sets of video cameras which are synchronized with each other. Parametric study reviles the effects of two key fluid properties: kinematic viscosity (or molecular weight) for silicone oil and density (or concentration) for sodium chloride aqueous water. After the withdrawal of a vertical partition plate, two liquids intersected earlier at the center, while the fluids stuck on the walls. The kinematic viscosity and density difference affect the three-dimensional mixing and stratification processes significantly. These visual databases are suitable for a code validation on the interfacial phenomena. Computational multi-phase fluid dynamics analysis was conducted with Star CCM+ version 8.04. The numerical results agree with experimental results accordingly for all those key parameters. The physics behind the contact angle and interfacial tensions are thoroughly investigated parametrically.