Dear Mr/Ms xxx(要写全名),
i am hornorable to invite you to attend xxx(写清楚邀请参加的是什么). Please see below for detail information:
Venue:xxx(这里写地点)
Date：xxx（这里写日期）
time:xxx（这里写开始时间）
I appreciate that if you could reply me whether you are going to come or not.
Best regards!
XXXX(写自己名字)