The non-linear dynamics inside the micro-fluid are visualized using the Micro-PIV technique. In the micro-fluid, the effect of interface/surface force is most dominant than the gravity or pressure. The flow filed can be determined with the balance between the viscous force and interfacial force, resulting in the highly non-linear flow field to be appeared. The non-linear flow field in the micro channel of 100um width was visualized by the Micro-PIV. The unbalance between the two fluids was explained using the interfacial force gradient.