This paper introduced the basic characters of the Trojan Horse technology briefly, and analyzed the implantation, startup and concealing in three important scenes of the technical implementation and features by analyzing the attacking means of Trojan Horse technology. The paper analyzed the files concealing, process concealing, concealing of communication with external in detail, while introduced some common Trojan Horse concealing modes with examples. In conclusion, the paper introduced several effective Trojan Horse defending tactics pertinently.