Jung Jo-gook scored twice while Yun Il-lok, Everton Santos, Sergio Escudero, Lee Seok-hyun and captain Koh Myong-jin were all on target at Seoul World Cup Stadium as FC Seoul comfortably secured a third consecutive appearance in the group stage having also reached the semi-finals last year.
But FC Seoul must now turn their attentions to next week's trip to Tianhe Sports Centre Stadium next Wednesday for their Group H opener against China's Guangzhou Evergrande, the side they lost the 2013 final to on away goals.
"We prepared really hard at the winter camp and it paid off," said coach Choi.
"The important thing is we have to forget about the last match and prepare for the next game.
"We have an away match against Guangzhou and I know they are really strong team. They have a strong squad, however, in football, we don't know anything until the final whistle," he added.