The invention discloses a dynamic RSA encryption method for an Ultralight radio frequency (RF) card through a time stamp. The method comprises the following steps: recording current time as the time stamp; encrypting the time stamp through AES to obtain time stamp ciphertext; carrying out specific operation on the time stamp to obtain a public key satisfying the RSA algorithm; reading an ID numberof the Ultralight RF card; encrypting the read ID number through the public key to obtain ID number ciphertext; carrying out accumulation and operation on the time stamp ciphertext and the ID numberciphertext to obtain CRC data; and writing the time stamp ciphertext, the ID number ciphertext and the CRC data into a data area of the Ultralight RF card. The invention further discloses a corresponding dynamic RSA identification method for the Ultralight RF card through the time stamp. The encryption method and the identification method provided by the invention have the advantage that the cracking difficulty and the safety of the Ultralight RF card are improved.