Alcaraz broke in the first game and looked comfortable throughout his 6-2, 6-2 victory.
Teenager Shang became only the second Chinese player to win an ATP Tour singles title at the Chengdu Open last month, but he was unable to make much headway against the world number two.
Despite their enthusiasm for Shang, the crowd couldn't resist Alcaraz's charm.
At the Spaniard's encouragement, they broke into loud cheers when he won a particularly exciting rally in which he hit a tricky backwards shot to keep the point alive.
"I've been playing really good tennis lately so I want to just keep going and keep feeling it, keep feeling this good," Alcaraz said after the match.
"I just had one practice then was straight into this match, so to be able to show this level in the first match, I'm just really proud," he added.
The Spaniard came into the tournament on a nine-match winning streak, having just won the China Open in Beijing, defeating top-ranked Italian Jannik Sinner in the final.
Sinner is also in action on Saturday, facing Japan's Taro Daniel.
