In order to comprehensively play various functions of online monitoring system of tailing dam,it is necessary to supply warning values of monitoring items of the system. Among all the items ,the warning value of seepage line and dry beach can be gotten on basis of seepage theory and limit equilibrium theory and its calculation process can be realized by geo-studio2007's relative modules. The seepage line can be computered in SEEP/W module and the situ stress can be computered in SIGMA/W module, and safety factor be in SLOPE/W module.It can be decided whether to warn by comparing the safety factor with the standard value.This is a calculation process of cycle search. The standard value of safety factor can be extracted from two documents of Safety technical regulations for the tailings pond（AQ2006-2005）and Design code for rolled earth-rock fill dam（SL274－2001）.All of the monitoring items is reasonable to use three grades warning. The warning values of seepage line and beach width of a grade five tailing dam were calculated through above the process. The effect of these warning values are good now.