Silica glass has long been considered to be the ideal materials in the situations demanding high ultraviolet or infrared transparency, and especially in some harsh environmental conditions for its excellent optical properties.However, strong absorption would occur when the glass is exposed to ionizing radiation such as gamma ray, x-ray, electron and ultraviolet light, which would limit the application of silica glass in radiative environment (space environment and nuclear reactor).Based on the former investigation, this optical degradation is closely related to the color centers and the OH content in silica glasses, but till now, the mechanism of coloration and the effect of OH groups on radiation-induced defects are not thoroughly known.In this work, color centers induced by gamma radiation in silica glasses with various OH contents are investigated.Several measurements, UV-Vis absorption spectra, electron paramagnetic resonance and Fourier Transform Infrared spectra were performed after the glasses being irradiated by gamma rays.And the dose ranges from 100kGy to 1000kGy.The results show that in all samples, E centers (≡Si*), oxygen deficient centers (≡Si-Si≡) and B1 centers are induced, while non-bridging oxygen hole centers (≡Si-O*) and aluminum-oxygen hole centers (≡Al-O*) exist only in low-OH JGS3 and medium-OH JGS2.The concentration of each color centers in high-OH JGSl is lower than that in JGS2 and JGS3.The kinetics of color centers between these three silica glasses are also different.In JGS1, color centers increase linearly with dose, while in JGS2, the defects grow in polynomial law and in JGS3,the exponential law was found.The phenomenon that different type and kinetics of induced color centers depending on the amount of the OH in the glasses is discussed.Through the recombination with atomic hydrogen released by photolysis of hydroxyl,the color centers named E center, non-bridging oxygen hole centers and aluminum-oxygen hole centers, could be transformed into visible colorless groups such as Si-H, H-bond Si-OH and Al-OH, which could be a good explanation for the suppressing effect of OH on the radiation coloration.This investigation will be of great importance to clarify the coloration mechanism and for the further guidance of manufacturing radiation-hard silica glass.