Due to complex and multivariate characters of the modern warfare, the commanders are required to improve their ability of making decisions quickly. Based on the research on warfare simulation and deduction system, the differences between real-time situation and off-line simulation deduction systems are analyzed. And the operation deduction method, the deduction system frame, and the situation capturing and processing technology are studied respectively. As for uncertain target types of the situation information, a new KNN (K-Nearest Neighbor) algorithm is proposed to match with unknown target models. The resulting product has been applied to one theatre command information system.