回複：請給30天往返美國不需簽證的官方連接，多謝！

These are from many school's international advisor:
The "automatic revalidation of visa" benefit allows most employees with H-1B status to return to the U.S. from a trip to Canada or Mexico (only) for 30 days or less without having a valid H-1B visa stamp (see exceptions below). The employee must have an old (expired) visa stamp from any status, a passport valid at least 6 months into the future, and the original H-1B approval notice (Form I-797). Automatic revalidation applies only to re-entry to the U.S. It may be necessary for you to obtain a Canadian or Mexican visa stamp for entry into those countries.

Exceptions: Citizens of Iraq, Iran, Syria, Libya, Sudan, North Korea, and Cuba are no longer permitted to take advantage of automatic revalidation. Citizens of these countries will not be permitted to re-enter the U.S. without a valid H-1B visa stamp.

Note: Any nonimmigrant who chooses to apply for a new H-1B visa in Canada or Mexico and is refused a new H-1B visa or has an application for a new H-1B visa pending will not be able to re-enter the United States using automatic revalidation. When applying for a visa stamp in any country, there is always a risk of being delayed for security clearance. For more information read the next section: Travel Resources- Post-Sept. 11 security issues .

These are the actually docuemnets.
Links

Department of State Official Public Notice - interim rule regarding automatic revalidation (pdf - Requires Adobe Acrobat) http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=2002_register&docid=02-5325-filed.pdf

Traveler from Canada, mexico
http://travel.state.gov/visa/temp/without/without_1260.html#information

Restriction
http://travel.state.gov/visa/laws/telegrams/telegrams_1441.html