Williams, who lives an hour's drive from the Tennis Center at Crandon Park and considers the tournament her home event, treated the second ranked Li like an unwelcome guest, needing just two hours on a steamy centre court to collect her 59th career title, the $787,000 (£473,000) winner's purse pushing her career earnings over $55 million (£33 million).
In 14 appearances at the Miami event Williams has driven back to her Palm Beach Gardens home with the trophy half the time, her seven titles two better than the five each she has won at Australian, US Open and Wimbledon grand slams.
After watching Li's forehand return slam into the net to end the contest, a delighted Williams danced around the court, raising seven fingers in the air signaling each of her Miami titles.
"I was actually super excited at the end, because I remember sitting here last year trying to get to six, obviously I wanted seven but I don't want to put the pressure on myself to get to seven," said Williams, who had shared the tournament record of six titles with Andre Agassi. "I wanted to have the most titles here.
"I guess that I've grown up coming to this tournament as a kid, watching so many players and to be one of those players now is really, really awesome for me."
While Williams was critical of her performance earlier in the tournament, calling it unprofessional, the 32-year-old American has been at her best against top players, winning 15 straight over top 10 opponents.
"I feel like when you're going up against the top players, for me, I have to be ready because they are the best in the world, the whole planet," said Williams. "So you have to be ready to play.
"I enjoy playing people that are ranked like that because I feel like I can eventually bring out the best in me."
A minority owner in the National Football League Miami Dolphins, a smiling Williams stepped out onto centre court to wild applause from the home crowd dressed in the orange and turquoise colours of her team.
The ovation, however, failed to inspire Williams as a determined Li seized the early initiative, breaking the American to open the contest and again in the seventh game to storm to a 5-2 lead.
But with Li serving for the set, Williams made her stand, overwhelming her Chinese opponent by sweeping 11 of the next 12 games.
"I don't think I was playing bad," said Li. "Maybe she just started to play a little bit better after 5-2 down.
"I don't think today I was doing a wrong game plan or I was play totally wrong.
"I think it was pretty good match."
Williams launched her comeback by fighting off two set points to record her first break at 5-3 and broke again at 5-5 to get back on level terms against an unsteady Li.
A screaming, fist-pumping Williams, now in top gear, held serve to take the lead for the first time and then added one more break to steal the first set from a crumbling Li, who was now in full meltdown.
Williams may have needed a while to warm up on a hot humid afternoon but once on track there seemed little Li could do to derail the 17-times grand slam winner.
Li held her opening serve of the second set but a ruthless Williams moved in quickly to deliver the knockout punch roaring through the next five games.
"I definitely don't do it on purpose," said Williams when asked about her slow start. "Everyone comes out there, they come really strong.
"Sometimes I do get off to a slow start, but then again, sometimes I get off to a fast start.
"I think for the most part, I try to do the best I can and sometimes things I'm doing don't work out, but they are the right things and eventually they start to work."
- Sports & Recreation