The 29-year-old, who won silver in the same C1 discipline in Beijing four years ago, had to pull out an impressive second run to qualify in a time of 92.83sec, good enough for fifth overall.
The Aberdonian came into the race as the world No.1, meaning he was scheduled last to run in the heats, but a poor first attempt put him down in 13th overall with only the top 12 going through.
The noise in the Lee Valley Arena was cacophonous as Florence began his second and final run of the day, knowing that he had to produce his best to keep his Olympic dreams alive, and he admitted that he had probably frayed a few nerves in his supporters' box before finally sealing his passage.
"I'm sure that all my family and friends were a little bit worried," he said. "I was certainly under a bit of pressure after a not very good first run but I've been in situations before where I've needed a good second one.
"But this is a pretty special atmosphere, I've not been in anything like this before and I've never gone last as world No.1 before either. I have never heard noise like that, it was just amazing, and I knew I had to just focus on it gate by gate and it was good enough.
"The course is very fast and it's got tough bits all over it that can catch you out so if things start to get on top of you it's hard to get the run back together. But it's the same for everyone, a lot of good runs were going in and I knew I needed a pretty good one to go through."
Florence is competing on two fronts at London 2012 with the C2 discipline, alongside Richard Hounslow, starting today. Having one job out the way, at least for the moment, the 29-year-old admitted that he was now fully focused on qualifying in the double discipline as well.
"The C2 is going to be a good race," he said. "It's something I'm really looking forward to and I'm focused on that now. Now I know what the atmosphere is going to be like, I'm more used to it and hopefully that will stand me in good stead for the rest of the races."
n Bank of Scotland, proud supporter of Team GB and proud partner of the London 2012 Olympic Games. Get closer to the Games at bankofscotland.co.uk/London2012
Contextual targeting label: