Untrusted hardware environment of computer system can give rise to untrusted software system. This paper puts forwards a trusted channel model and firmware based on trusted platform control module. This model constructs a kind of trusted channel between trusted platform control module and hardware device through trusted micro command to put down hidden dangers such as data being monitored, tampered and forged in the process of transmission. Besides, this paper constructs varied trusted channels applied in different situations in accordance with needs. Finally, trusted channel is proved to show inconspicuous effect on hard disk read / write efficiency, hence can be applied widely in current trusted computer system.