While Li easily outshone his nearest rivals to grab the top prize in both the vault and parallel bars, Russian diva Svetlana Khorkina failed in her bid to win the beam title with a scrappy display of balancing skills.
Li, having claimed gold on the vault an hour earlier with an aggressive 2 1/2 twisted front somersault, executed a dynamic swinging routine on the bars.
Incorporating a number of impressive handstands, the 21-year-old edged out Slovenia's Mitja Petkovsek by just 0.025 of a point.
A product of the famed Hunan Gymnastics School, Li went into the parallel bars final as the overwhelming favorite following his triumph on the apparatus in Sydney two years ago.
Backed by a boisterous Chinese contingent, a steely eyed Li mounted the bars and put in a near flawless performance.
Having completed his display with a solid dismount, he cracked a broad grin and punched his fists toward a sea of red and gold Chinese flags fluttering at one end of the Fonix Hall.
"In the morning I was still struggling with a cold and did not feel great at all, but as soon as I stepped into the arena, everything felt great," said the soft-spoken Li.
"My nerves and aches all just disappeared suddenly and my batteries were completely recharged for the competition. It's a fantastic feeling to have won two gold medals."
Russia's Khorkina, who suffered her first asymmetric bars defeat at a major event for eight years on Saturday after falling off twice, was hoping to redeem herself on the beam.
Although she did not fall off the apparatus, unlike in the first round of qualification, she struggled to keep her balance on several occasions to ruin her chances.
Despite knowing she was not going to have a prized medal gleaming around her neck, the elegant Russian did not flee the arena as she had on Saturday.
With her blonde hair pulled back into a ponytail, Khorkina's trademark smile was back in place on Sunday as she circled the arena signing autographs.
With her contenders failing to execute their programs cleanly, an ecstatic Ashley Postell became the surprise winner of the beam.
Postell's winning score of 9.537 gave the Americans their second title at Debrecen after Courtney Kupets scored a shock victory on the asymmetric bars on Saturday.
"This is my first major championship, I'm a rookie as they say," the jubilant 16-year-old said.
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