be afraid of sb/sth 害怕某人/某物,后接名词或代词
be afraid to do sth 害怕做某事,后接动词
希望我的回答能够帮到你,那不是还有一个be afraid of doing sth.的么？be afraid of doing sth 是“唯恐做某事”的意思，或者说担心某事会发生，不是有没有胆量的问题，这点与be afraid to do 不同。如 He was afraid to walk across the bridge because he was afraid of falling into the river.“他不敢过桥，因为他怕掉进河里”