Abstract: The method based on energy deposition to analyze the influence of -ray radiation on fiber refractive index was proposed. The fiber dispersion variable which changes with the fiber V parameters and refractive index was analyzed and calculated. The radiation effects on fiber dispersion measurement experiments were accomplished, which demonstrates that the radiation impact on the presence of fiber dispersion. The fiber dispersion coefficient variation data with radiation dose were obtained. Experimental and theoretical results show that:(1) fiber dispersion coefficient increases with radiation dose, within the dose range of(0-500 Gy) fiber dispersion coefficient showed a gradual increase in the amount of saturated trends; (2) changes in the refractive index of the fiber lead to the additional material dispersion. The electron density increases caused by radiation is the major factor that results in changes in the refractive index; (3) the decrease of ultra-fast pulsed signal amplitude caused by radiation-induced loss is more significant than pulse broadening caused by radiation-induced dispersion. Both effects exist simultaneously. The pulsed signal distortion is the result of two joint action of especially for long distance optical fiber with nuclear radiation exposure.