【Purpose/significance】Data mining technology becomes one of the common counter-terrorism methods that can be used to analyze the various daily lives of terrorists, such as logistics, the flow of money, the flow of information, etc.【Method/process】This paper will propose how to use decision tree of information gain to classify the information of terrorists quickly. The classification begins from the attribute of root and continue to generate new branches. Every branch selects forked attribute by comparing the information gains of different attributes.【Result/conclusion】Through combining with other data mining methods, decision tree of information gain will increase efficiency of intelligence analysis and improve the mechanism of terror threat warning. This method can be used not only in the undergraduate education, but also in training intelligence analysis.