stop doing sth.是停止做某事
e.g.Hearing the doorbell,she stopped washingthe dishes.
听见门铃声,她停止洗碗了.
stop to do是停下（手头的事情）去做另外一件事
e.g.Hearing the dollbell,she stopped to open the dor.
听见门铃声,她停下手中的活去开门.