Abstract: The application discloses a light scattering parameter measurement system and its measurement method. Dual-frequency scattering interference technology is adopted to obtain distributed measurement of Rayleigh scattering parameters in an optical fiber. The Rayleigh scattering coefficient r and phase retardance ? are modulated on different components of the interference signal respectively by using the dual-frequency interference technology. The Rayleigh scattering coefficient r and phase retardance ? can be decoupled by simple filtering, to obtain separate measurements. A linear stretch is applied to the optical fiber under test, to add uniform phase change signals at all positions of the optical fiber under test. As a result, the term containing only Rayleigh scattering coefficient r can be extracted by low-pass filtering. The direct measurement of Rayleigh scattering parameters is of great significance to fundamental and application researches related to Rayleigh scattering of optical fiber.