Two years ago the canal boat was still running but I've heard rumours since then that it doesn't operate anymore. I never heard a good thing about it when it was running.

I personally think Suzhou is worth more than 1 day so I'd stay the night and head for Hangzhou by bus on day 2.

Bus may also be a quicker way to reach Yiwu since the motorways are efficient in Zh.

overnight boat is meant to save time, i once took a bus tour to wuzhen from shanghai, the bus actually took most of time(i sent about 1 hour plus a lunch there :(). so, sounds like my plan is not practical. if boat from suzhou to hangzhou is not available, i may just skip suzhou and take shanghai-hangzhou-yiwu-shanghai i think shanghai to yiwu train should pass hangzhou, or there is better way? thanks

If you have only 5 days, and need to spend 1.5 days in Yiwu (therefore only 3.5 days left for the rest), then you'd better skip Suzhou. I'd give 2 days to Shanghai and 1.5 days to Hangzhou.

What dates will you be travelling on? What times are you arriving and leaving Shanghai?