There are many groups of rebels who had used naked women to fend off firepower of government troops since the late Ming. This magic method--Yin-men- chen--was practiced up to the Taiping rebels and Boxers of the late Ch'ing. For example, The nurse, who took care of the famous writer-Lu Xun, when he was a little boy, told him the following story about her own experience with the Taiping rebels: "When government troops of Ch'ing came to attack the city, the Long Hairs (the Taipings) would make us take off our trousers and stand on the city wall, presuming that the cannon could not be fired; if fired, it would burst!" The story is very interesting. There are many similar cases in late Imperial China. This thesis will re-explore the relations between women's body and warfare through Yin-men-chen. Previously, some scholars had discussed the topic, such as James Parson, Sawada Mizuho, Soda Hiroshi, Li Jianmin, and Paul A. Cohen. Based on their researches, this article will re-explore the topic in two aspects: women's body and cannon, and women's body and magic power. Topics examined in this paper include: (l)What are the features of Yin-men-chen? (2)Why can women's naked body fend off firepower? (3)What kind of Women has the potentiality--power of resisting firepower? We suggest that naked women, above all, menstruating women, was a symbol of pollution, which would negate the power of cannon as well as black magic.