An index system for structure safety assessment was presented on the basis of analyzing and comparing of the domestic and foreign researchers. In addition, a method for structure safety measurement using Bayesian network, which has the excellent abilities of expressing and reasoning knowledge under uncertain environment, was proposed to construct a safety assessment model afterward. The assessment model is able to deal with complicated relationship as well as the different opinions of experts. The output of the safety assessment model can be used to predict and diagnose different safety conditions. Finally the model is applied to evaluate the security level of a certain overhead traveling crane.Its results show this method is effective and reasonable.