Amusan broke the world record earlier on Sunday by running 12.12 in the semi-final at Hayward Field.
She recovered from a slightly slower start to put on a pristine performance over the barriers, .17 seconds clear of silver medallist Britany Anderson of Jamaica.
"The goal was to come out and to win this gold," said Amusan.
"I believe in my abilities but I was not expecting a world record at these championships. You know, the goal is always just to execute well and get the win. So the world record is a bonus."
Puerto Rico's Olympic champion Camacho-Quinn accelerated at the midway mark but lost a close battle with Anderson over the final strides after hitting the last hurdle, going home with bronze in her first World Championships.
"I got my nerves to be honest. It kind of showed on my face but I am just glad to come out here," said Camacho-Quinn.
"From this point on, it is only going to be faster ... I think we had the best event of the whole world champs."
Anderson told reporters she was pleased with her performance, despite clipping some hurdles.
"I feel like everyone is so excited now," she said. "I came out here to do what I had to do and I did it."
The final was without 2019 champion Nia Ali and medal contender Alaysha Johnson, both of the United States, after they hit hurdles and crashed out in the opening round. read more
The United States' Olympic silver medallist Kendra Harrison, whose 2016 record Amusan broke in the semi-final, was disqualified.
Amusan’s world record in the semi-final stunned the athletics world.
“Wow” tweeted sprint king Usain Bolt, while 200m champion Noah Lyles tweeted: "Are you kidding me?"
Amusan said she was shocked to have produced the record in the semi-final but knew she had it in her.
"I could not believe it when I saw it on the screen after the semis. But it was just a matter of time," she told reporters.