Unlike H1B holder who can be allowed to work for up to 3 years at a time, H1B1 holder may be allowed to work in US for up to one year at a time, but you can extend your H1B1 status before your H1B1 I-94 expires or change your H1B1 to H1B.
这样说来是不是每年都要续签?
-Yes, your employer file I-129 within US.
持有H1B1签证的最多可以工作几年？
-Total 6 years (H1B1, or H1B1 plus H1B).
是不是必须在一年后当签证需要续签的时候就可以要求换成H1B?
-Yes, you can when the H1B quota are avaible (e.g. on/After April 1 each year)
还有这一年的签证可以多次自由出入美国（比如出差）而不需要重新签证吗?
-H1B1 visa normally is valid for 18 months with multiple entries, so you can go out of US and reenter US using this visa. By the way, visa (stamp on your passport) is different from status (I-94 duration).
再次感谢耐心的回答。
