The present invention disclose a key distribution method. The method includes obtaining, by a first key management system, a shared key of a first network element, where the shared key of the first network element is generated according to a key parameter obtained after the first network element performs authentication or a root key of the first network element; obtaining a service key, where the service key is used to perform encryption and/or integrity protection on communication data in a first service between the first network element and a second network element; performing encryption and/or integrity protection on the service key by using the shared key of the first network element, to generate a first security protection parameter; and sending the first security protection parameter to the first network element. According to present invention, data can be protected against an eavesdropping attack in a sending process.