This paper analyzes the characteristics of borehole losses during drilling caused by varied geological conditions such as leakage, intermediate and tiny fissures, large karst caves leakage and ruptured cracks. Then it evaluates the dilation property of the hydration expansion composite material system and the plugging effect of the composite bridge sealing method from the modeling and mine experiments. The results show that plugging material PAR has a highly absorbent property and can be expanded to several times the original size and can form the plugging quickly.