Abstract: For the difficulty of measuring the thin film thickness, a method of thin film thickness measurement based on laser heterodyne interferometry was proposed. Using the classical Michelson interference optical path, the heterodyne interference principle was used to convert the film thickness difference into the optical path difference, and the precise displacement table was used as the scanning mechanism to realize the progressive scanning measurement of the film thickness. Results show that the shift of the measurement system within 20 min under constant temperature experimental conditions does not exceed 8 nm, and the average deviation of the measurement results is less than 1 nm. Comparing with the measurement results of the ellipsometer, the measurement difference is 12.97 nm, indicating the feasibility of the method.