Abstract: In order to measure the velocity history of the reflected surface or the internal particles velocity history of the materials under shock wave conditions,on the basis of the frequency-selecting principle of F-P optical resonator,a new type of velocity interferometer is developed,which makes use of the absolute magnitude of Doppler shift to continuously measure the moving of a flyer speed.The flyer is driven by a electric exploding foil,the magnitude of its speed can reach up to 3km/s within 60ns.Preliminary results show that the uncertainty in data is less than 5%.Compared with other laser interferometers,the lately developed thin cavity interferometer is compact,simple and low cost.So it can be widely used in the detonation and shock wave physics experimental research.