My wife is a Chinese National with Canadian Permanent Resident. I am Canadian.

We are planning to travel to China and HK next month. We will land in Shanghai then fly to Hainan then fly to Guangzhou and take the train into Hong Kong. We will depart fo Canada from Hong Kong.

My question is does my wife need a HK visa when we plan to stay there less than 7 days before departing back to Canada?

Here is what it says on the HK government website:

3. PRC passport holders who are in transit through the HKSAR to and from another country or territory may be granted a stay of seven days on each landing without the prior need to obtain an entry permit provided that usual immigration requirements are met, including possession of valid entry facilities for the destination and confirmed onward booking for the overseas journey.

Anybody know?

from the wording, it sounds like she can stay for 7 days without any issue. as long as she has proof of departing flight and she can legally enter canada.