The invention relates to a device for generating sub-kHz low-frequency intensity difference compression based on a cesium atom ensemble and mainly aims at solving the technical problems of high priceand large volume of an existing low-frequency compression state device. According to the technical scheme, the device for generating the sub-kHz low-frequency intensity difference compression based onthe cesium atom ensemble comprises a semiconductor laser, a single-mode optical fiber, reflectors, an optical beam splitter, an electrooptical modulator, a fabry-perot etalon group, lens assemblies,half-wave plates, a Glan laser prism, a cesium atom pool, a Glan-Thomson prism, a beam collector, a high-frequency signal generator, photoelectric detectors, a subtracter and a spectrum analyzer, wherein the semiconductor laser is arranged on the surface of an independent heat insulation platform; and a heat insulation cover covers to isolate the semiconductor laser and the platform from the external environment. According to the device, the low-frequency intensity difference compression of which the maximum compressibility is 6dB-1kHz can be obtained, the device is stable in performance and compact in structure and commercial production can be achieved.