的大侠提供我备份的

美方机构出具的正式聘书（写明工作内容、职位、聘用期限并承诺帮助进行豁免申请及转签证等内容）。老板给写封推荐信就可以了, 主要写明帮助豁免申请及转H签证.只要简单地写几行就可以了.
这封信只是写给中国大使馆的, 美国国务院不要这封信

Sample

To Whom It May Concern:

This is to certify that Dr. xxx holds a Research Associate appointment
in xxxx Department at the University of xxxxx. He has been making excellent progress on his research project, which I am directing. Because he has recently been making some important breakthroughs that will take some more time to bring to full fruition, he would benefit greatly by being able to continue here for one (or two) more year. Consequently, we would like to request a change from his current J-1 to an H-1 visa Status.


Very truly yours,

Xxx