With the popularity of the research and use of cloud computing, the use and understanding of cloud computing become deeper and deeper, therefore, people's attention and exploration has been sparked by the importance of cloud computing security. This article mainly analyzes the cloud computing security of Hadoop environment, and studies the factors which affect the security of cloud computing, starting from a specific environment. Finally, this paper puts forward an improved Deterministic Packet Marking (DPM) algorithm to improve the security of cloud computing from the aspect of the network.