Abstract: Security issues in cloud computing are not all technological, rather, it is the issue of reliability, confidence, and lack of clear and enough information about cloud security. In order to improve the security of heterogeneous independent cloud environments, a novel cloud dependability model named CDMV (cloud dependability model by virtualization techniques) is proposed by using virtualization techniques. Our contributions can be summarized as follows: a general formal CDMV model with good scalability by using system-level virtualization techniques for cloud systems is proposed, and systematic analysis on how CDMV model can enhance the system dependability is presented; the proposed CDMV construction is equipped with the definition of dependability in cloud systems and a series of quantitative indicators to evaluate the dependability, which are missing in most existing schemes.