Bolt improved his personal best time this season by 0.03 seconds but was still well short of his world mark of 9.58 seconds.
“Overall, technically wise, it was a good race,” Bolt said. “It was not the best start, but I executed well overall.”
Nesta Carter of Jamaica was second in 9.90 seconds ahead of Michael Rodgers of the United States, who was third in 9.96.
Bolt’s last race before the worlds, which start August 27 in Daegu, South Korea will be a 200 at Stockholm next week.
Bolt had to battle all the way to prevail against a strong field that also included European champion Christophe Lemaitre of France and Jamaican Michael Frater.
On a very fast track and with a slight tail wind, the triple Olympic champion failed to beat the Herculis meet record of 9.82 after surging ahead of his rivals in the last 20 meters.
“Nesta Carter, Michael Frater are very good starters, better starters than me,” Bolt said. “But the last 60 (meters) are the best part of my race, so I was never really worried. Overall it was good.”
Bolt, who competed for the first time on the Stade Louis II track, is unbeaten this season and said winning races, even by small margins, is the most important thing ahead of the worlds.
“For me it’s always key to keep winning,” he said. “And I’m getting better. My last 60 meters have improved dramatically. I need to work on my reaction time, but I’ve been doing great in training, so I’m just focusing and I feel ready.”
Frater was fourth in 10.01 while Lemaitre ended fifth in 10.03.
Bolt, who has been hampered by injuries last season, has already warned he won’t lower his 100-meter world record this year and that he is only focusing on defending his sprint titles in Daegu.
“My aim this season is to run 9.7, maybe 9.6,” he said. “For me, this year it’s about building myself and go into the Olympic season fit and ready. London is the key.”
In the men’s 800, world record holder David Rudisha of Kenya improved the season-best time he set last month, winning in 1:42.61.
Rudisha, who was hampered by tendinitis in his left foot earlier this season, stayed close to his usual pacemaker Sammy Tangui in the first lap before pulling away from the pack.
Asbel Kiprop of Kenya produced a great effort in the final stretch to close the gap but had to settle for second with a personal best time of 1:43.15.
Nick Symmonds of the United States finished third, in 1:43.83.