Concerning the problem that the communication keys in transmission of mission planning system were easily stolen in White-Box Attack Context (WBAC), a new secure transmission method of mission planning system was proposed based on modified white-box Advanced Encryption Standard (white-box AES). First, the Advanced Encryption Standard (AES) was split into many lookup tables and the keys were embedded into these lookup tables, then the lookup tables were merged in accordance with the excuting order of the AES. Secondly, on the ground, different white-box AES programs were generated in accordance with the given white-box AES generation algorithms using different keys. In the end, the white-box AES programs were embedded in the security transmission of the mission planning system. When the key needed to be replaced, the original white-box AES program should be erased on the ground to generate a new white-box AES. Theoretical analysis shows that compared with the traditional secure transmission of mission planning system, the modified secure transmission method of mission planning system can make the attack complexity to 2 ⁹¹, which achieves the sufficient security and can protect the communication key.