Method for establishing a trust chain, comprising: requesting a third CA for a third key pair and a third certificate, writing a private key of the third key pair and the third certificate into a security storage area, the third certificate comprising model information of the smart television (SMTV) terminal and information of a public key of the third key pair. The SMTV terminal check its possession of a fourth certificate on every start, generate a unique fourth key pair in absence of a fourth certificate, submit online a public key of the fourth key pair and a unique identification of each SMTV terminal to a fourth CA to request for a fourth certificate, and send along the third certificate and a signature signed on the request with the private key of the third key pair; write the fourth certificate into the security storage area upon receiving the fourth certificate.