be in agreement on和be in agreement with的区别在于介词on和with后面的宾语不同，所以意思也就是不同的。
1. be in agreement on：对某事意见一致；就什么事情达成一致意见。
这是一个系表结构，系动词加介词短语；
介词on 后面接达成协议的内容、方面。相当于agree on。
例句：
An agreement on many aspects of trade policy was in sight.
有关贸易政策诸多方面的一项协议即将签订了。
But it was noticed that these two were never in agreement.
但很显然他们两个从来没有过一致的意见。
The one thing everyone is in universal agreement on is that what happened was extraordinary.
所有人都普遍同意的一点是，这里发生的事情是不同寻常的。
2. be in agreement with，与……保持一致；同意。
这也是系表结构；系动词加介词短语，介词with后面接名词、代词。
例句：
He is in agreement with our plan.
他同意我们的计划。
Our plan is in agreement with his.
我们的计划与他们的一致。
The experimental demonstration is in agreement with the theory.
实验结果与理论分析相符。