Abstract: In order to investigate the effect of the high-order dispersion on the gain spectra of cross-phase modulation(XPM) instability under different incident optical power,starting from the coupled nonlinear Schrdinger equations of two optical waves in an optical fiber and utilizing the linearorder stability analysis,the gain spectra of cross-phase modulation instability varying with the incident optical power was calculated when the second-order and the fourth-order dispersion coefficients have the same,opposite signs and when the second-order dispersion coefficients was equal to zero,respectively.The mechanism behind these diverse spectra was analyzed in detail.The results show that,when the second-order and the fourth-order dispersion coefficients have the same sign,with the increase of the incident optical power,the gain spectrum which consists of two separated regions first,will broaden and combine to one region.When the second-order and the fourth-order dispersion coefficients have the opposite signs and the second-order dispersions are equal to zero,the gain spectrum consists of only the first spectral region near the zero point.Moreover,the width and the peak value of the gain spectrum will increase with the incident optical power.The investigation can be a theory guidance to generate ultrashort optical pulse chains with high repetition rate to some extent.