1.be afraid of doing sth意思是“害怕某事会发生”,重点在“怕”；
be afraid to do sth意思是“（因为害怕而）不敢做某事”,重点在“不敢”.
2.如：The little boy is afraid to return home because he is afraid being beaten by his father.
这个小男孩因为害怕会被他老爸打,所以不敢回家.
如果写成：The little boy is afraid of returning home because he is afraid to be beaten by his father.就很搞笑了：
这个小男孩因为不敢被他老爸打,所以害怕会回家.
3.另外,还有be afraid of sb/sth的用法“害怕某人/物”,但是后者只有be afraid to do sth“不敢做某事”.