Beauchemin-Nadeau, a silver medallist four years ago in New Delhi, finished with a combined total of 250 kilograms, a Games record in the 75-kilogram division.
"I knew the record was attainable, and I knew that I was aiming for it even on the first lift," she said. "I was prepared for this."
Beauchemin-Nadeau lifted 110 kilograms in the snatch and 140 kilograms in the clean and jerk.
"It was a great afternoon, I was very happy with my performances," she said. "My preparation for the competition was quite hard, but I worked a lot over the last couple of weeks. I was aiming for the record and for the gold medal, and I'm very happy I've got both.
"I've built up my confidence with this competition."
Mary Opeloge of Samoa was second with a 243-kilogram total. She was hoping to beat Beauchemin-Nadeau's 140 with her final lift in the clean and jerk but walked away from the 141-kilogram bar without making an attempt.
Apolonia Vaivai of Fiji took the bronze with 209 kilograms.