【Abstract】 Objective To study the synergistic mechanism of synergistic rodenticides, and to observe the pathological changes in rodents tissue so as to provide the evidence for its application. Methods The effect of synergistic rodenticides to CT, PT, APTT and FIB were evaluated at the condition of SD rat as a model. The pathological changes in the tissues were detected by paraffin slice and HE staining technique. Results Single synergist could prolong CT and APTT and also increased FIB. While both warfarin and synergistic warfairn could obviously prolong CT, PT and APTT and reduced FIB. Compared to warfarin, the synergistic warfairn could increase CT, PT and APTT and reduced FIB. The histology and pathology observation indicated that synergistic warfairn could lead to a peptic ulcer compared with warfarin. It also led a pneumorrhagia and necrotic liver in toxic rats. Conclusion It suggests that synergist has an anticoagulant function, and the anticoagulant role of synergistic warfairn is powerful than that of traditional warfarin. Synergistic warfairn also leads to internal hemorrhaget and other physiological disfunction, while single synergist does not cause the histopathological damage.