A security authentication method, device, and system are provided. A first device and a second device perform security authentication by using a first mapping key and a second mapping key, where the first mapping key is generated according to an initial key of the first device and a first predetermined algorithm, the second mapping key is generated according to an initial key of the second device and the first predetermined algorithm. A device in embodiments of the present invention performs security authentication by using a mapped initial key, which can increase the difficulty for an attacker to acquire a key, thereby improving security of a wireless network connection.