Just two days after their explosive 100m showdown at the Bird's Nest in which Bolt came out victorious by just one-hundredth of a second, the Jamaican clocked 20.28 seconds to win his heat.
Bolt eased up with fully 50 metres to go after he came off the bend ahead of the field in a first successful step in his bid to retain his world sprint double.
Gatlin, who has served two doping bans and whose defeat by Bolt was heralded by some as symbolic given the doping issues in which track and field finds itself mired, dominated his heat, winning easily in 20.19sec.
Also going through will be Japanese teenager Abdul Hakim Sani Brown, the 16-year-old clocking 20.35sec behind Gatlin in an impressive first outing in the worlds.
The semi-finals are scheduled for Wednesday and the final on Thursday.