Abstract: The durability of shotcrete and rockbolt support system has direct influence on structure stability and operating life in tunnel and underground engineering projects with composite lining. Anchor system, which is mainly made of steel elements, is readily subjected to corroding. Based on the structural features of the tunnel and underground engineering project with composite lining, it can be deduced that the erosion of a bolt can be mainly attributed to the interaction between the anchor system and erosive underground water from wall rocks. In this paper, the dominant factors, influencing the erosion of anchor system of underground structure in sulfide-bearing wall rocks are discussed, especially the formation of erosive underground water in wall rocks and the physico-chemical mechanism for the erosion of a bolt under this condition are described. Based on this mechanism, and a method for estimating the operating life of an anchor system in sulfide-bearing wall rocks is proposed.