The world number 10 was in ferocious serving form, striking aces up to 112 mph against the shell-shocked Majoli.
After winning the first set on a tie-breaker, Williams then stepped up a gear in the second, losing only one game before wrapping up the match.
"I was very comfortable with my serve today," said the fourth-seeded Williams, who received a first-round bye.
"I served pretty well in the first few games of the first set and I did well in the second set and that was really key and important for me, to make sure I'm serving well."
Williams will now face 15th seed Barbera Schett in the third round.
The Austrian beat Thailand's Tamarine Tanasugarn 6-3 6-2.
Seeds progress
Other seeded players into the third round included Amelie Mauresmo, Jelena Dokic and Meghann Shaughnessy.
Yugoslav, Dokic, made light work of Magui Serna of Spain 6-1 6-4, while third seed Mauresmo saw off Russia's Elena Likhovtseva 6-0 6-3.
American Shaughnessy, seeded ninth in Toronto, defeated Shinobu Asagoe of Japan 6-0 6-4.
But 16th seed Chanda Rubin had to withdraw from her match against fellow Amy Frazier with a sprained ankle while trailing in the third set.
Qualifier Wynne Prakusya Indonesia will face Jennifer Capriati after the number one seed beat Meilen Tu 7-6 3-6 6-3.