中位线定理在解题中具有广泛的应用,是平面几何中的一个重要定理.在同一个题设下,包含两个结论.分别是两线段所在直线的位置关系(平行)、两线段的数量关系(倍半).同时,需要根据具体情况按需选用这一定理,不一定同时需要两个结论,有时需要平行关系,有时需要有倍分关系.本文根据题设的若干情况举例说明了中位线的构造方法. The median line theorem has a wide range of applications in solving problems and is an important theorem in plane geometry. In the same subject, it contains two conclusions: the position relationship (parallel) of the line where the two lines lie, the two lines Need to use this theorem according to the actual situation, not necessarily need two conclusions at the same time, and sometimes need parallel relationship, and sometimes need to have a multiple relationship.This article illustrates the situation based on a number of situations The construction of the median line.