"be surprised at" 和 "be surprised to" 的区别在于后面跟的名词或动词不同，表达的意思也略有不同。
"be surprised at" 后面跟名词或代词，表示被某个具体的事物或事件所惊讶，例如：
I was surprised at the news of his resignation.（我对他辞职的消息感到惊讶。）
She was surprised at her friend's sudden change of mind.（她对她的朋友突然改变态度感到惊讶。）
"be surprised to" 后面跟动词不定式，表示对某个行为或情况感到惊讶，例如：
I was surprised to see her at the party.（我看到她在派对上感到惊讶。）
He was surprised to hear that he had won the lottery.（他听到自己中了彩票感到惊讶。）
需要注意的是，有些情况下，两种表达方式是可以互换使用的，例如：
I was surprised to find out that she had moved to France.（我发现她搬到了法国，感到惊讶。）
I was surprised at the news that she had moved to France.（我听到她搬到了法国的消息，感到惊讶。）
但是在一些特定情况下，两种表达方式的意思是不同的，需要根据具体语境来判断。
"be surprised at" 和 "be surprised to" 的区别在于它们所表达的意义不同。
"Be surprised at" 意为“对...感到惊讶”，强调的是惊讶的对象，即导致惊讶的原因。
例如：
I was surprised at the news of his resignation.（我对他辞职的消息感到惊讶。）
He was surprised at the price of the car.（他对这辆车的价格感到惊讶。）
而"be surprised to" 则表示“感到惊讶（因为发生了某件事情）”，侧重于惊讶的人的感受和态度。
例如：
I was surprised to hear that he had resigned.（听说他已经辞职，我感到很惊讶。）
She was surprised to see me.（看到我，她感到很惊讶。）