This paper presents amethod to detect the displacement of the interference stripe in LD interference field soas to get the information of LD frequency fluctuation. The Michelson interferenceapparatus is chosen in the laboratorial device. CCD is used to sense the displacementsignal of interfernce stripe in the interference field. After corresponding circuitprocessing, the useful signal then is input to a computer. At last, the frequencyfluctuation of LD can be detected.