Qin and Luo romped to victory with 463.98 points to give the hosts a perfect six golds from six finals after Shi Tingmao had earlier won the women's one-metre springboard gold.
Beijing Olympic gold medallist Qin has now won three successive world titles in the men's three-metres springboard synchro event, though the previous two world championships and the Olympic gold were with Wang Feng.
Russia's Ilya Zakharov and Evgeny Kuznetsov clinched silver after scoring 100.32 points with their final dive to finish on 451.89 while Mexico's Yahel Castillo and Julian Sanchez took bronze (437.61).
Shi's victory was the fifth of the competition for the Chinese after she totalled 318.65 points. Compatriot Wang Han finished second (310.20), while Italy's Tania Cagnotto clinched bronze (295.45).
Britian's Keri-Anne Payne led from start to finish to claim the world swimming championships women's open water 10km gold medal on Tuesday, the victory ensuring she qualified for next year's London Olympics. The 2009 world champion and Beijing Olympics silver medallist completed the four laps of the Jinshan City Beach course in two hours, one minute and 58 seconds, seeing off every challenge thrown at her and somehow finding another gear to extend her lead.
Italy's Martina Grimaldi finished second while Greece's Marianna Lymperta finished third.
Russia won their third successive synchronised swimming team technical gold medal with a high tempo routine that earned sustained applause.
