H1B 有效期一般是一年，最多是三年。 H-1B visa is an employment-based nonimmigrant category for foreign workers. H Visa holders can work only on that particular position and there are no option to change jobs within the same employer or different employers with out having a new H visa petition filed by the company in front of USCIS office， i.e all changes need to be approved by USCIS officers (USCIS Officer will review petitions where employee has request for Change of Employer). There must be at least one year between each H visa period， so you cannot stay less than this amount of time unless your case is being reviewed for approval.
There may be other exceptions/ waivers if requested as well e.g if a situation requires the worker to leave the U.S.， such as vacation etc；or job transfer from overseas to U.S. If you do not have sufficient working experience to qualify you for the next level then we advise filing for O-4 extension， which would allow you to remain until you meet the requirements. This type of application involves more paperwork but it does mean greater security. In some cases， however， certain circumstances could lead us to file for green card without prior H status.
