这里有一个模板可以参考一下
Dec 7, 2014
U.S. Embassy
Beijing, China
RE: Visitor Visa Application for (dad's name) and (mom's name)
Dear Immigration Officer,
My name is (my name). I am writing this letter in support of my parents' application for a visitor visa.
I am a Chinese national. Currently I work for (company name) as a software engineer. My wife and children also are living with me in (city). I am on H1B status and my wife H4 status. Enclosed please find copies of our H1B/H4 approval notices.
We invited our parents to visit us and enjoy the beautiful summer here in (city). During their stay here, we will fully support them including all their living and travel expenses. Attached please find a copy of my recent pay stubs reflecting my ability to support them.
Thanks in advance for your courtesy in this matter and we look forward to seeing our parents soon.
Sincerely,
(your name)
(address)
Home Phone: (xxx) xxx-xxxx