The analysis and research described in this paper aim at solving the problem of data confidentiality and fault-tolerant in cloud storage environments. It first shows that the existing solutions can either solve the problem of confidentiality or fault tolerance, but are not able to take both for consideration. In order to solve the problems, the paper proposes a secure cloud storage system with data confidentiality and fault-tolerant (SCSM-DCF)，which is based on threshold public key encryption scheme and erasure codes over exponents. The formal definition, security definition, and communication protocols between entities are given in this paper. Finally, the performance of the model is analyzed, and the result indicates that the model is not only correct and secure, but also has the higher efficiency.