The invention discloses a method for realizing network data security of an alternating current/direct current control protection system. The method comprises the following steps: performing position replacement on a generated secret key according to a bit position by using a preset replacement algorithm, and encrypting a load and a signature of a message by using the replaced secret key and a preset encryption algorithm to form a ciphertext; receiving the message, restoring the dynamic secret key through a preset inverse permutation algorithm, and decrypting the ciphertext through the restoredsecret key and a preset encryption algorithm to obtain a message load and a signature by the receiving end; and when the received message is verified and signed, carrying out signature verification on the restored secret key and the decrypted message load by using a preset signature algorithm. According to the method, the network message in the system is controlled and protected to realize encrypted transmission, and a device outside the system cannot analyze the content after intercepting the message, and cannot forge the message to be injected into the system, so that the security of network data in the system is ensured.