Abstract: According to mechanical and structural characters of an externally prestressed box girder with corrugated webs, and mechanical performance such as load bearing mechanism and mechanical characters, the damage form and ultimate load capacity of concrete block deviator used in externally prestressed box girder with corrugated webs are studied using FEA and experimental methods. Experiment and FEA results fit each other well. The research indicates that the local influence caused by a deviator in concrete flange concentrates in the joint of the deviator and concrete flange and its nearby location, the damage of the deviator is caused by concrete tension damage and reinforcement tension yield, the round reinforcements show obvious characteristics of an eccentric tension member.