To improve the accuracy of the safety assessment, this paper constructs the cloud security evaluation model. It obtains the  evidence of the evaluation respectively from the host security, data security, physical security, network security and application security, using limit of machine learning algorithm. Data mining and membership degree method is used for data standardization and index weight calculation, finally obtaining the cloud security assessment. The experiment proves that the constructed cloud security evaluation model can quickly obtain the evaluation evidence of the cloud security evaluation index system, and make the evaluation results scientifically and comprehensively, reflecting the comprehensiveness of the evaluation.