Abstract: The application of oil film interferometry (OFI)technique at Ma=8 was conducted in the Φ0.5m hypersonic wind tunnel.Accurate viscosity coefficient of the oil film was derived from the viscosity-temperature curve by analyzing the infrared images which were recorded simul-taneously with the fringe pictures.Based on the marker spots,the relationship between infrared images and fringe pictures was figured out.A test of skin friction measurement on a flat plate model using OFI technique was conducted.The results show that the standard derivation of the measured viscosities to the mean value is less than 10%.Test results are consistent with the the-oretical estimation according to boundary layer theory for laminar flow on a flat plate.