如果只是noon，那么就只有at noon这一种表达方式，on noon是错误的。如果有表示具体某一天的noon，那么就用on，例如：在周一中午on Monday noon。例句：The long day of meetings started at noon.会议接连不断的漫长一天从中午开始。
noon造句
1、The workers quit work at noon.
2、The ultimatum expires at noon tomorrow.
3、In the sweltering haze of summer-noon.
4、The vast silence of noon hangs over the sea.
5、You must check your luggage in before noon.