Abstract: This paper points out the deficiency in detecting the unknown Trojan horse of the present anti-virus software at first, introduces the advantage of artificial immune system in self-adaptability aspect, and points out the feasibility of artificial immunity mechanism in Trojan horses detection; Then through an analysis about the new technology of Trojan horses, proves the deficiency of current computer security system with a Trojan horses model, presents the transfer of Trojan horses detection from the anti-virus software to the subsystem of immune IDS, improves the self-adaptive capacity of Trojan horses detection with its immune mechanism; Finally, a behavior mode is put forward, which is mapped from the using situation of process systematic resource to the process systematic call, and by this means, a Trojan horse detection model based on artificial immunity mechanism is set up.