Originally Posted by jiejie

That is a workable plan, there's no "quota" of total transit days per time period. Booking a flight to/from HK in the middle of that stay is OK and maybe less hassle than getting a visa. However, think about what you are proposing with respect to The Big Picture. You will spend more, possibly a lot more, on the flights Shanghai-HK-Shanghai than you would on just getting a new Chinese visa. And it breaks up that time in China awkwardly, which could be used for daytrips or overnights to other cities in the greater Shanghai/Jiangsu area.

Unless you specifically WANT to go to HK on this trip, I'd advise just getting the Chinese visa, which should be gettable as a 12-month multiple entry type.