Well in English, both words could be interpreted as 'exicted'. Usually when we use 兴奋, it refers to a situation in which we are also kind of encouraged. To be simple, it is often used in positive conditions. e.g.我收到了盼望已久的礼物，感到很兴奋。 I am excited when I recieved the gift which I wish for. However, 激动 can be used when you are talking about someone who is too happy, to excited or to angry.

興奮以英語解釋就是excitation。 但激動是有兩個解釋，其中一個用法就是可以表達跟興奮差不多的意思。 如：他們因為贏得了世界杯冠軍而感到既興奮也激動。 在這個例句中，興奮和激動的意思其實差不多，都是想表達因為某一件〝好〞事情而感到情緒高脹。 而激動的另一個意思即英語的agitation。這往往是指因為發生某些壞事情，讓你情緒瞬間變得忿怒和衝動，想幹什麼事來報復對方。例如：Susan's son was killed in a car accident. She was in great agitation and wanted to kill the driver as a revenge.

簡單地來說 興奮：開心 激動：感情受激動

If you only use them as a adj,they have the same mean.I looked up the chinese dictionary,the expanation of "兴奋" is just "激动". Usually there is some satisfied things that can make a person "兴奋" , but when coming a bad news a person may be "激动" 而不用“兴奋”. I wish my word can help u understand this two words better.

兴奋 指的是极度的开心（very very happy）而激动指的是由于受到刺激而感情冲动 例如：我的心情很激动。但不能说 我的心情很兴奋 “兴奋”is more excited than “激动”