The relationship between fluorescence lifetime and OH groups concentrations in theN2122andN3122phosphate laser glass used in the Shenguan Facility is investigated experimentally. We also study experimentally and theoretically the influence of fluorescence lifetime and loss on gain property in phosphate glass. It is shown that to increase fluorescence lifetime of glass can effectively improve the gain property. When fluorescence lifetime of glass adds 10 percent, its gain coefficient will increase 5 percent. We also measured the gain of two groups glasses (4 samples) with different fluorescence lifetime and loss under the same pump condition. The results indicate that in case of keeping the gain property unchanged, we can increase its fluorescence lifetime and reduce its loss requirement.