演绎推理法是指人们以一定的反映客观规律的理论认识为依据,从服从该认识的已知部分推知事物的未知部分的思维方法。本文以本人开设的高中化学“知识拓展类”选修课“氮及其化合物”为例,从化学的普遍性规律出发,就如何运用演绎推理法,演绎推导出“未知”物质的组成、结构、性质及制备来进行教学作一阐述,以起抛砖引玉之用。 Deductive reasoning refers to people’s thinking method of inferring the unknown part of something from the known part obeying the knowledge based on certain theoretical knowledge reflecting the objective law. Based on the general rules of chemistry, this article takes the high school chemistry “knowledge expansion class ” elective “nitrogen and its compounds ” as an example to deduce “unknown ” on the basis of the deductive reasoning method. Material composition, structure, nature and preparation of teaching to make an elaboration, in order to serve as a starting point.