回复：加拿大绿卡的好处：H1B到期后用加拿大永久居民的身继续在美国

No such benefit. The only benefit that Canadian PR has is having chance to get long term, multi-entry visa instead of short term one issued to Chinese resident with mainland Chinese passort.

After 6 years H1b, you must leave US for at least 1 year before you can come back with a new H1b. Or you may try to switch to other visa status such as F1, L1, O1 etc.