Abstract: Frequency-shifted feedback laser based on acousto-optic modulation was one research hotspot in the current, and it can produce a string of harmonic wave with same interval frequency. In order to generate multi-frequency laser, the frequency-shifted feedback laser method was adopted to design an all-fiber frequency-shifted amplified feedback loop. A theoretical model of laser heterodyne correlation was established and the numerical simulation was carried out. At the same time, a fiber amplifier was introduced into the loop, and the influence of gain coefficient on the corresponding intensity of each harmonic was studied. The selection of different gain parameters for each order frequency was verified. The results show that, frequency-shifted feedback loop could be used to achieve the high-frequency modulation, several times of the fundamental frequency modulation. The highest modulation frequency is up to 4GHz. The study lays the theoretical and experimental foundation for the research of the new system of high-frequency modulation laser.