Aimed at the issue about the targets detection and classification in target monitoring system based on WSN, the study proposed a multi-sensor data fusion method based on intuitionistic fuzzy reasoning (IFR). The property functions of two status variables were designed according to the method of fuzzy reasoning. The study constructed the inference rules of the system after acoustic energy attenuation model and the variety of magnetic field model were built, and the rationality of constructed rules was checked. The comparison between theoretical analysis and simulation result show that intuitionistic fuzzy reasoning can classify targets uncomplicatedly and effectively. Because of its less calculation, the method can apply to WSN node, in which the calculation capacity is weak.