The invention provides a cloud data security realizing method based on tail-cutoff survival, comprising the following steps: a service system receives a data access request of a user and then transfers the data access request to a cloud storage platform; step 2, the cloud storage platform calls a data malicious access detection software module to analyze whether the access is a malicious access; step 3, when finding a malicious access behavior, the data malicious access detection software module calls a data tail cutoff software module to handle the malicious access behavior; step 4, the data tail cutoff software module interrupts the current malicious access behavior of the service data; and step 5, when data tail cutoff operation is completed, a data regeneration software module is called to recover backup data. When data is maliciously accessed, copied, modified, deleted or illegally operated by other means, data loss is avoided to the maximum based on the principle of tail-cutoff survival, and the security of the data is protected.