The Calgary slider finished in a track-record time of four minutes 30.31 seconds with teammate Chelsea Valois of Zenon Park, Sask., for her 12th-straight podium finish.
"I'm ecstatic," the reigning Olympic champion said. "Our goal all year was to win world championships and we did it. This is the perfect end to a great season and to do it in St. Moritz is the ultimate for any bobsledder.
"People don't understand what this place means to us athletes. It is the birthplace of our sport and the longest track in the world that demands experience and skill so it means the world to me to win the world championships here."
Leading by 0.12 seconds after Friday's two runs, the 27-year-old Humphries and the 25-year-old Valois opened up a half-second lead heading into the fourth and final run down the only non-refrigerated track in the world, and built on it — besting the field by nearly seven-10ths of a second.
Elana Meyers and Katie Eberling of the United States won silver with a time of 4:30.99, while Germany's Sandra Kiriasis and Franziska Bertels took bronze in 4:31.01.
Edmonton's Jenny Ciochetti, who pushed Humphries to her first world championship in Lake Placid, N.Y., last year, drove the Canada 2 sled to 18th place with Calgary's Kate O'Brien.
It is Humphries' 10th victory in her last 12 international races dating back to last year. Her only two detours to the winner's circle were a silver medal last week in Igls, Austria, where she missed gold by .01, and a bronze earlier this the month in Altenberg, Germany.
Humphries has welcomed three different brakemen into the Canada 1 sled on her remarkable golden run, including Valois, who got introduced to the sport just this fall.
"We learned last week that every hundredth-of-a-second matters so we just wanted to focus on pushing as hard as we could and not hold anything back," said Valois. "I'm overwhelmed. It feels amazing and has been quite a year for sure."