In the public cloud computing environment, users can not control the storage position of the data effectively, so it can not guarantee the security of userÂ data and there is a big security risk. In order to ensure the security of userÂ core data in cloud computing, this study proposes the idea of hybrid cloud architecture in terms of protecting the security of userÂ data and designs a userÂ core data protection model based on cloud computing. It decomposes the data on the basis algorithm and the data after decomposition are the core data and general data. When the general data is handled by the gateway filtering, the data which is blocked is stored in the private cloud and the data which is not blocked is stored in the public cloud; when storing the core data, the security and privacy of these data should be protected. These data is stored in the private cloud or stored in the public cloud with encryption. Although there are many studies on the application of cloud computing, it is still in the development stage and the problem related to data security has not been solved effectively. And from the perspective of cloud computing users, this problem needs a long-term concern. The security of the core data can be effectively protected after processing. This study designs data classification algorithm and selects of existing mature network products to build out the core data protection system of enterprises based on cloud computing. And the system is applied to an enterprise for one-year experiment to verify the validity of the model. This study is expected to explore new ways to protect the userÂ core data based on cloud computing.