Abstract: The decline of mucus viscosity is a common problem in the manometry process of apron mucus sealing device and capsule mucus sealing device. The factors of mucus viscosity reduction include the permeability effect, the decomposition of bacteria, and influence of high-pressure gas environment, underground water pH value, the influence of the temperature of the underground, hole sealing time and influence of decomposition in mucus itself. Through the homemade device which can measure mucus viscosity in high-pressure environment, the change rules of mucus viscosity in different conditions are determined, and the experimental analysis of various influence factors of mucus viscosity are carried out. Finally, the best scheme to stabilize mucus viscosity is found, which is used in coal mine site and some improvement effect is got.