Four-time European champion Illya Kvasha of Ukraine took silver with 434.30, while Alejandro Chavez of Mexico won bronze with 431.55.
"When I was young my coach gave me a video about the Olympic Games in 1992," Li said. "I remember I have a dream I can stand in this pool.
"So today my dream came true and I won the championship. I feel this pool is amazing. Actually Spain is very lucky for me. Since 2005 I have been here seven times. It's like here is a second hometown. In China somebody called me 'King of Spain.'"
China has won seven of the last eight world titles in the event and two of the three in diving so far at the world championships.
Matthieu Rosset of France finished only 0.5 points behind Li in the preliminaries Saturday. Rosset looked to be in contention when he entered the fifth round in the lead, but he blew his entry and Li nailed a difficult inward pike with 2½ somersaults for the highest single-dive score of 86.70 to take command.
Rosset, who was aiming for France's first diving medal at worlds, finished in sixth place.
With Kvasha pushing, the 25-year-old Li still had to execute a tough forward pike with 3½ somersaults on the last dive of the final to ensure he retained his title.
China has won gold in three of four diving events so far at Montjuic Municipal pool, with its picturesque views of the Catalan capital.
On Saturday, Wu Minxia and Shi Tingmao won the women's 3-meter synchronized springboard. The next day, China's run of three consecutive world titles in the men's synchronized 10-meter platform was broken by German pair Sascha Klein and Patrick Hausding.
Chen and Liu built an unassailable lead by executing five nearly flawless dives to earn 356.38 points, giving China its seventh consecutive world title in the event. Chen's fourth straight victory at worlds in this event added to her four Olympic gold medals.
Olympic bronze medalists Meaghan Benfeito and Roseline Filion of Canada took silver with 331.41 points. Malaysia's Pandelela Rinong and Mun Yee Leong were 0.27 behind to claim bronze, the same medal they won at the 2009 worlds.