Chen, 19, was celebrating long before he crossed the line in an Olympic record time of one hour 18 minutes 46 seconds, 11 seconds ahead of Barrondo and Chinese Wang Zhen.
Russia's Olympic and double world champion Valeriy Borchin collapsed into the side railings due to exhaustion on the last stretch and received medical treatment.
The Chinese duo of Chen and Zhen, who won this year's world race walking cup, jostled for position with Russia's Borchin and Vladimir Kanaykin for long parts of the race, first reeling in Japan's Yusuke Suzuki and then Frenchman Bertrand Moulinet who had both tried to go early.
Chen made his break for gold around the 18km mark but silver and bronze were still to up for grabs for the chasing pack of five until the final stages of the race.
In quick succession, Colombia's Luis Fernando Lopez and Kanaykin were disqualified before Borchin's race ended with him crumpled on the floor and looking dazed.
Not concerned with the chaos behind him Chen felt confident enough to enjoy his first major title five minutes before he had secured it, wagging his fingers in the air to the delight of the crowd.