A refractive index measurement method and an experimental system based on spectral domain interference have been established, which mainly includes a fiber-optic Michelson interferometer, a spectrometer, linear fitting and phase unwrapping methods. Interference signals are collected by the spectrometer, and high-precision optical path lengths are obtained using linear fitting and phase unwrapping methods, thereby calculating the refractive index. Using this system, the refractive indices of silicon wafers, N-BK7 glass, and distilled water are measured to be 3.511±0.012, 1.508±0.019, and 1.311±0.022, respectively. The relative errors are 0.23%, 0.33%, and 0.37%, respectively. This method enables refractive index measurements of transparent and translucent solid and liquid samples without the need for special sample treatment, showing a new development and application of interferometry technology.