In view of the fact that the quantum computer attack is not considered in the cloud storage environment, this paper selects the code-based public key encryption scheme as the security protection measure in the cloud storage. Based on random linear code encryption scheme, it employs the structure of the RLCE scheme and Polar code polarization properties, using the Polar code as underlying encoding scheme, through the method of RLCEspad, putting forward a kind of improved public key encryption scheme which considers semantic security and is resistant to adaptively chosen ciphertext attacks. The improved scheme is applied to cloud storage to ensure that the storage environment will not be attacked by quantum computer while ensuring the confidentiality, availability and reliability.