Abstract: Dependability evaluation is an essential issue for Internetware which is in open, dynamic and decentralized Internet environment. But dependability is generally evaluated by simple metrics based on black box without considering system structure in many cases. In this paper, an evaluation model of dependability for Internetware based on Bayesian network is proposed. It builds a multitier dependability evaluation metrics system by structure analysis and structure pattern of Internetware. It uses bottom-up approach on the basis of Bayesian network to calculate dependability metrics of Internetware system and its components from many aspects. A unique dependability metrics is obtained and amended by objective data as a result. Experimental results show that the model can evaluate dependability of Internetware clearly and objectively. It also contributes to design, development and deployment of Internetware.