Chinese star Wu lifted his fifth DP World Tour trophy just six days short of 10 years since his maiden triumph, which came at this event in 2015.
Wu was on the edge of contention after reaching the turn in 34, but five birdies on his back nine saw him power to the top of the leaderboard with the lowest round of the day to reach 14 under par.
Englishman Jordan Smith, who was among five players to share the lead in a chaotic final round at Enhance Anting Golf Club, birdied the last hole to finish one shot adrift of his 39-year-old playing partner.
Smylie was the best-placed Australian, finishing eight shots behind in a tie for 15th at six under after carding rounds of 67, 70, 71 and 70.
Compatriot Jason Scrivener, who also opened with a brilliant 67, then had rounds of 71, 73 and 73 to finish in a tie for 43rd place at even par.
"It is very special, that was 10 years ago when I won the Volvo China Open in Shanghai," Wu said.
"To come back to Shanghai and win again, it is a great story.
"It was a great round, I played great golf this week. You are always happy to win your own country's open, so very, very exciting.
"It's an incredible week, there are incredible fans here and lovely golf course. It's my home, Shanghai, even after a couple of rounds I felt relaxed because I was playing at home. Shanghai has given me luck."
Overnight leaders Li Haotong and Eugenio Chacarra, who was bidding for back-to-back DP World Tour titles after success at the Hero Indian Open, finished in a tie for fourth with China's Dou Zecheng at 11 under.
Ding Wenyi shared a tie for eighth as four Chinese players made the top 10 for the first time in the event's 30-year history.
