The Dayaoshan Tunnel is located in the Nanling Mountains at the north part of Guangdong Province. It is the longest double — track railway tunnel in China with a total length 14. 295km. The burst mud and spring water occuried during the tunnel construction. According to the meteorological data for many years, the construction observation and the tectonic analysis，the authors calculated the maximum spring water yield of an adit and fore?cast the main spring water location in the karst region，considering that the karst spring wa?ter in the middle part of the tunnel is the confined ground water in a deep karst region， meanwhile the spring water in the quartz—sandstone area at the exit direction belongs to the type of the most abundant ground water in a fault zone. The spring water is separated by the fault 9，but also had some connection in a whole.