The design and construction of the large piperoof advance reinforcement applied in the treatment of the karsts in Nanshan tunnel are presented in the paper, with the emphasis being placed on the presentation of the construction process, safety control measures and effect assessment of the large piperoof reinforcement. The engineering practice proves that the large piperoof advance reinforcement technology is effective in the treatment of the filling karst caves. The successful engineering experience can provide reference for similar works in the future.