A cloud storage method, applied to a terminal side of a cloud storage system, the terminal side comprising a cloud storage client, a key management terminal and a quantum key distribution QKD system, the method comprising: generating, by the QKD system and a QKD system on at least one cloud server side, at least one quantum key over a quantum network (S101, S201, S301); sending, by the QKD system, the at least one quantum key to the key management terminal for storage (S102, S202, S302); obtaining, by the cloud storage client, the at least one quantum key from the key management terminal, and processing the at least one quantum key to generate a combined key by a predetermined encryption algorithm (S103, S203, S303); wherein the method is characterized in that it further comprises: encrypting, by the cloud storage client, to-be-stored plaintext data with the combined key, to generate ciphertext data (S204, S304); sending, by the cloud storage client, the ciphertext data to the cloud server side for storage (S205, S305); deleting, by the terminal side, the at least one quantum key and the combined key (S206, S306); sending, by the cloud storage client, to the cloud server side a download request for requesting to download the ciphertext data and the at least one quantum key; receiving, by the cloud storage client, the ciphertext data and the at least one quantum key fed back by the cloud server side; processing, by the cloud storage client, the at least one quantum key by the predetermined encryption algorithm, to generate the combined key; and decrypting, by the cloud storage client, the ciphertext data with the combined key. generating, by the QKD system and a QKD system on at least one cloud server side, at least one quantum key over a quantum network (S101, S201, S301); sending, by the QKD system, the at least one quantum key to the key management terminal for storage (S102, S202, S302); obtaining, by the cloud storage client, the at least one quantum key from the key management terminal, and processing the at least one quantum key to generate a combined key by a predetermined encryption algorithm (S103, S203, S303); wherein the method is characterized in that it further comprises: encrypting, by the cloud storage client, to-be-stored plaintext data with the combined key, to generate ciphertext data (S204, S304); sending, by the cloud storage client, the ciphertext data to the cloud server side for storage (S205, S305); deleting, by the terminal side, the at least one quantum key and the combined key (S206, S306); sending, by the cloud storage client, to the cloud server side a download request for requesting to download the ciphertext data and the at least one quantum key; receiving, by the cloud storage client, the ciphertext data and the at least one quantum key fed back by the cloud server side; processing, by the cloud storage client, the at least one quantum key by the predetermined encryption algorithm, to generate the combined key; and decrypting, by the cloud storage client, the ciphertext data with the combined key. encrypting, by the cloud storage client, to-be-stored plaintext data with the combined key, to generate ciphertext data (S204, S304); sending, by the cloud storage client, the ciphertext data to the cloud server side for storage (S205, S305); deleting, by the terminal side, the at least one quantum key and the combined key (S206, S306); sending, by the cloud storage client, to the cloud server side a download request for requesting to download the ciphertext data and the at least one quantum key; receiving, by the cloud storage client, the ciphertext data and the at least one quantum key fed back by the cloud server side; processing, by the cloud storage client, the at least one quantum key by the predetermined encryption algorithm, to generate the combined key; and decrypting, by the cloud storage client, the ciphertext data with the combined key.