求异面直线距离是立体几何的一个重点和难点 ,而将其转化为求线面距离和面面距离则是常用的两种转换思路和方法 .但现行的立体几何教材中却没有安排专门的内容介绍这两种转换方法 ,那么教学中何时向学生渗透这两种转化思想较恰当呢 ?笔者认为 ,如能结合教材第一章最后一个例题 Finding the straight line distance from different sides is a key and difficult point of the three-dimensional geometry. Converting it to the line distance and the distance between faces is a commonly used two kinds of conversion ideas and methods. However, there is no special arrangement in the current three-dimensional geometry textbooks. The content introduces these two kinds of conversion methods. So when is it appropriate to infiltrate these two kinds of conversion ideas into students? The author thinks that if we can combine the last example of the first chapter of the textbook