你可能agree to一个东西，但是你不一定agree with它。
1.“agree to do sth”表示“同意做某事”
不定式 to do 含有“要去做......”的含义，所以，agree to do 就是同意去做什么事，例如：
What on earth had possessed her to agree to marry him?
究竟是什么让她同意嫁给他的？
You and I are going to have to agree to disagree then.
那你我只能各自保留不同意见了。
The undersigned buyers agree to pay a 5,000 pound deposit.
已签名的买主同意支付5,000英镑的订金。
She agreed to have a swim with me. 她同意和我一起游个泳。
Did you agree to come with him? 你同意跟他一块去了吗？
当agree to中to作介词时，含义为：接受、认可，常常指并非出于主观愿望的“同意”，尤指不乐意或经过争论之后的同意（含有未必赞成的意思）；agree to后常接建议、计划、安排等如：
At last his wife agreed to the trip if he allowed her to go also.
终于他老婆同意了这次旅行，条件是她被允许一道前往。
Those who agree to this plan please put up their hands.
同意这个计划的，请举手。
I cannot but agree to your decision.
我不得不同意你的决定。
The enemy is so desirous of peace that he will agree to any terms.
敌方急欲求和，什么条件他都会答应。
We will agree to disarming troops and leaving their weapons at military positions.
我们将同意解除军队的武装并把武器留在军事阵地。
The management is understood to be very unwilling to agree to this request
据了解，管理层很不乐意答应这项要求。
I was forced to agree to it, but at heart I didn’t quite agree with it.
我被迫答应，但内心并不完全同意。
He said all that remained was to agree to a time and venue
他说剩下的只是商定一个时间和集会地点。
《柯林斯高阶英汉双解学习词典》
2. agree with指出自主观愿望的“赞成、接受、同意”，如：
I don’t agree with a single word that you have said.
你所说的每一句话我都不赞成。
In many ways I agree with his statement. 多方考量，我同意他的说法。
The great majority of people seem to agree with this view.
大多数人似乎都同意这种观点。
As the author of the proposal I cannot agree with you.
我作为提案的发起人不能同意你的意见。
I don't really agree with that.
对此我不太赞同。
I don't agree with you there.
在那一点上，我不敢与你苟同。
I don't altogether agree with you.
我不完全同意你的意见。
I entirely agree with you.
我完全同意你的看法。
I don't agree with spanking.
我不赞成打屁股。
In his heart he knew they'd agree with his stand.
他内心明白他们会赞成他的立场。
I completely agree with your recent editorial. 我完全同意你最近的社论。
agree with+人，表示同意某人的话，意见、看法、观点等
agree with+非人的成分，表示同意、赞成+接受
agree with还可以表示：与…相符（一致）;（气候、食物等）适合于
Your account of the accident does not agree with hers.
你对事故的叙述与她的叙述不一致。
His story agrees with the facts. 他的陈述与事实相符。
A verb must agree with its subject in person and number. 动词必须和它的主语在人称和数方面保持一致。
The weather doesn't agree with me.我没有适应这里的气候。
The food does not agree with me. 这食物对我不适合。
Hard work does not agree with him. 艰苦的工作对他不适宜。
The author can report other people's results which more or less agree with hers.
作者可以提及其他人得出的和她自己基本吻合的结果。
3. agree on表示：两方或多方就某事取得一致意见或达成协议；所以运用这个词组的时候，就必须是至少有双方或三方乃至多方才能一致意见或达成协议这个含义：
When did you last hear from Jay?
你最后一次听到杰的消息是什么时候？
He phoned me this morning, and we agreed on a time and place to meet.
今天上午他打电话给我了，我们就会面的时间和地点达成一致意见。
Can we agree on a date?
我们能否约定一个日期？
We rarely agree on what to do.
我们很少在要做的事情上看法一致。
The two sides failed to agree on the wording of a final report
双方未能就最终报告的措辞达成一致。
It took five months for the coalition to agree on and publish a medium-term
economic programme.
联合政府花了5个月的时间才达成并公布了一项中期经济计划。
'I think we could agree on that one.' — 'Only just.'
“我想在那一点上我们是一致的。”——“勉强算是吧。”
agree on后接动名词，表示同意做某事。如：
He agreed on helping us. 他同意帮助我们。
注：与 agree to do sth 大致同义。所以上句也可说成：
He agreed to help us.