Abstract: The paper introduced concepts of cloud computing and Internet of Things, analyzed inevitability and combination mode of the cloud computing and the Internet of Things. It proposed architecture of the Internet of Things based on cloud computing and studied security threats of the Internet of Things based on the cloud computing and gave corresponding security solution including how to construct trusted environment for the Internet of Things and how to protect data security in the cloud of the Internet of Things. It pointed out technical difficulties of the security research and research status of the Internet of Things based on the cloud computing.