The geology of the region which Baojianshan tunnel crossed through was very complex. The layer was consisted of broken phyllite which was easily softened with water. The rock mass had collapsed several times while excavation by the construction methods which designers offered. In this article, the sub-classification of phyllite was established according to State Standard Classification of Rock and Designing Standard of Railway Tunnel. Based on this sub-classification, a series of construction methods in phyllite were set up eventually. And Baojiashan tunnel was successfully built using the construction methods mentioned above.