1.accident指偶然发生的不幸事件,即“事故”；incident则指普通的小事件,也指暴力性的政治事件.如：
About ten people were killed in the car accident.在这次车祸中大约有10个人丧生.
That was one of the strangest incidents in my life.那是我一生中最奇怪的事情之一.
The book is about the July 7th Incident.这本书是关于七七事变的.
2.在习语 by accident (偶然地)中,不能用 incident.如：
I found the wallet quite by accident.我找到这个钱包纯属偶然.