The Athens gold medallist shot to the front in his first round heat on the opening morning of the championships then eased at around 60 metres to win in 10.16 seconds.
"I feel good," said Gatlin. "I will do whatever I have to do. If I have to break the world record I will.
"The track is very fast, I think it's easy and fast like in Athens, I think I can go even faster here than I did in Athens."
Gatlin, 23, is aiming for a 100-200 double after winning both events at the U.S. championships. His main rival Jamaican Asafa Powell, who reduced the world record to 9.77 seconds this year, withdrew this week with a groin strain.
"I think everyone is really prophesying that because Asafa is not here, I'm going to go and run away with it," Gatlin added.
"But anyone who steps up to the starting line in the final and comes home to the finish line has equal chances like I have of winning."
A further round is scheduled for Saturday evening followed by the semi-finals and final on Sunday night.
KLUFT TRAILS
France's Eunice Barber, the 1999 gold medallist, took an early lead on the first day of the heptathlon over defending champion Carolina Kluft of Sweden, who injured her left ankle in training on Friday.
Barber compiled 2,252 points from the 100 metres hurdles and high jump to lead the Olympic champion by 153
Kluft, the premier high jumper in the field, bowed out at 1.85, well below her personal of 1.94.
"I felt no pain from the hurdles but I was afraid to give it everything in the high jump," she said.
"It's too early to think about medals. There are five events left still and I'll take them one at a time."
John Godina's quest for a fourth world shot put title ended in the qualifying round when a daunting list of illness and injury caught up with the 33-year-old American.
"I had four injuries in eight weeks and pretty major illnesses," he said.
Godina, who had never before failed to reach a world final after winning the 1995 title, said he had suffered injuries to both elbows and his right hand. He had also been struck twice by a stomach virus that resulted in him losing five kg in weight.
Another athlete hit by injury, defending 400 metres hurdles champion Felix Sanchez, finished second in his first round heat but was in obvious pain after the race.
Sanchez, who has been fighting injury since failing to finish in the Brussels Golden League meeting last year after winning the Olympic title in Athens, said he would need surgery on his right foot.
"The injury is very painful," he said. "Three weeks ago I could not walk. But I'm in too good shape to stay at home."
