Under the environment of vacuum and cold black, the change in optical transmittance of JGS 3 optical quartz glass induced by radiation of protons with 140 keV was studied. When the radiation fluence exceeds 5×10 14 protons/cm 2, an absorption band in the wavelength range of 230～250 nm appeared and its peak increased with increasing the radiation fluences monotonously. Under higher radiation fluences, weaker absorption bands existed in the near ultraviolet and visible region. The color center E′ is responsible for the 230～250 nm absorption band. The E′ color center induced by proton radiation in the optical quartz glass is disturbed by hydrogen. During the radiation not only the breaking of Si-O bonds but also the transition from the and radicals into the and would occur.