常识性问题，给你个足够权威的说法：来自移民局

Who can an H-1B alien work for?

H-1B aliens may only work for the petitioning U.S. employer and only in the H-1B activities described in the petition. The petitioning U.S. employer may place the H-1B worker on the worksite of another employer if all applicable rules (e.g., Department of Labor rules) are followed. H-1B aliens may work for more than one U.S. employer, but must have a Form I-129 petition approved by each employer.


以上信息摘自

http://uscis.gov/graphics/howdoi/h1b.htm