The invention belongs to the information security technical field and provides a cloud storage data protection method and device. The cloud storage data protection method includes the following steps that: public keys transmitted by a cloud server are received, wherein the public keys transmitted by the cloud server are uniquely corresponding to user accounts logging in a client end; original data are uploaded to the cloud server, such that the cloud server can utilize pre-stored private keys to encrypt the original data, and generate encrypted data and save the encrypted data, wherein the pre-stored private keys are corresponding to the public keys transmitted by the cloud server; and the public keys transmitted by the cloud server are utilized to obtain the original data from the cloud server. With the cloud storage data protection method and device of the invention adopted, even if cloud storage data are disclosed, a third party is very difficult to obtain real data, and therefore, the security of the cloud storage data can be ensured, and the information security of cloud server users can be ensured.