Abstract: The traditional key expansion algorithm of the Advanced Encryption Standard(AES) is easy to be cracked under the condition that a certain round key is known. Through the research on the implementation method and the process of encryption and decryption algorithm, aiming at shortcomings of the key expansion algorithm are relatively easy to crack round key, by the methods of combine one-way strategy and random function, the key expansion algorithm is improved. And then simulation the algorithm through the Keil software in 24Mhz, The results show that this method is effective in ensuring the safety of the key expansion algorithm and can guarantee the efficient operation at the same time.