In this study, an interfacial temperature sensor, having a junction thickness of only 1 mum was developed utilizing micro-fabrication technique. As a simulation of rapid contact solidification process, a sudden falling experiment was conducted. The special sensor was employed to measure the rapid temperature changes at the substrate surface. A simple procedure was proposed for determining the interfacial thermal conductance during the rapid contact process of molten metal (Indalloy-158) with copper substrate. The influence of initial state of molten metal on thermal conductance was investigated. The agreement between the calculated thermal histories and measured ones indicated the validity of the present method.