sdfsdfsdff is correct. 由於北美自由貿易協議, 加拿大公民不需要簽證. 隻是在入境口岸申請入境. 也沒有30天的限製. 你去中國旅遊回來, 在入境口岸隻要出示I-797 原件就行. But it's also better to show two-months stubs, employer letter, etc.