Quartz crystal is the only time scale for laser ranging. Its stability directly affects the accuracy of ranging results. The Moisture content in quartz crystal has a great influence on the performance of crystal. The influence of different internal water vapor content on the performance of crystal devices at different temperatures is analyzed. The results show that the higher is the moisture content, the closer is the temperature to the limit, which influences on the quartz crystal seriously. Five cyclic processes are proposed such as removing moisture from the quartz crystal after baking for 0.5 hours in the baker with 125 ℃±5 ℃ before packaging, vacuuming repeatedly and refilling pure nitrogen. And the moisture content can be controlled below 2 000 ppm, and the purpose of reducing the water vapor content in the quartz crystal is achieved.