When two kinds of polarized light with different wavelengths are transmitted in optical fiber, cross-phase modulation instability may occur due to the commonness of cross-phase modulation and fiber dispersion. This phenomenon has important applications in optical switching, supercontinuum generation and other fields, and is also an important factor affecting the performance of WDM systems. Based on the nonlinear Schrodinger equation coupled by two optical fibers, the stability of light is analyzed linearly, and the dispersion and gain spectra of cross-phase modulation instability are derived. The variation of gain spectrum with dispersion parameters, nonlinear parameters and power is simulated. The results show that the peak intensity of pulse changes with the increase of power, and the peak value and broad spectrum are increasing. When other conditions remain unchanged and the dispersion parameters increase, the broad spectrum narrows and the peak value remains unchanged. Secondly, when other conditions remain unchanged and the nonlinear parameters increase, the spectral width is larger and the peak value is larger.