也有条款说不需要护照的,如果从美国直接去: http://cbsa-asfc.gc.ca/publications/pub/bsf5023-eng.html#s2x5
Permanent residents of the United States may travel to Canada from the
United States or Saint-Pierre and Miquelon without passports, travel
documents or visas provided they produce satisfactory evidence of their
identity and status.