The 29-year-old seventh seed, who has won the world title for an unprecedented five times, out-punched Japan's Ayako Minnowa 20-9 in her lopsided opener of the flyweight 51kg division after getting a first-round bye.
"It was such a confusing bout, I don't know how to describe it. My opponent was very strong but she had no skill or technique, she only had strength. She fought like a bull, only hitting my belly," Mary Kom said laughing while speaking to PTI from Qinhuangdao.
"I mostly used my left hook in today's bout. She was just so confused about what to do. Had I resorted to her tactics it would have become a street fight.
"I kept control over my temper. Told myself that I cannot attack like her so it was better to counter. It was very draining," added the reigning Asian champion who was facing the Japanese for the first time in her career.
Mary Kom will now square off against Marielle Hansen of Norway on Tuesday in the last-16 stage.
Hansen defeated Zaida Enriquez Cedillo of Mexico 21-7 in her opening bout.
"I am going to fight her for the first time. Let's see how it goes," she said. (MORE)