Abstract: Aiming at the deficiency of single effect quantity analysis method of high arch dam safety monitoring,we introduce a data fusion theory named D-S evidence theory into multi-effect quantity fusion model of high arch dam.A new formula for calculating the fusion coefficient is put forward suitable for D-S evidence fusion evaluation to high arch dam safety,and a multi-effect quantity fusion model of high arch dam is established based on improved D-S evidence theory.The results of engineering example indicates that this method is reasonable and feasible,which not only provide a new way for high arch dam multi-effect quantity comprehensive evaluation,but also can reduce uncertainty and unacknowledged in high arch dam safety evaluation.