The Bruins also defeated the Flames 4-3 in a shootout at Universiade Sports Center in Shenzhen on Saturday. DeBrusk scored the shootout winner.
DeBrusk missed time in the second and third periods because of a stomach illness. He left with 12:39 remaining in the second and didn't return until 2 1/2 minutes into the third period.
"He's growing as a player," coach Bruce Cassidy said. "We used him on the [penalty kill] the other night, a little bit tonight. He's a little more conscientious in that area, aware. A year under his belt, not surprised. But lots of pace to his game, good finish in tight. He showed a lot of that the second half of last year so good growth."
Tuukka Rask made 28 saves, and Kevan Miller scored an empty-net goal with 1:15 remaining for Boston.
Sean Monahan scored, and Mike Smith made 17 saves in his preseason debut for Calgary.
DeBrusk's second goal came from in front of the net at 5:27 of the third period. Jakob Forsbacka Karlsson, who was behind the net, put the puck in front and DeBrusk put it past Smith, who was turned around and couldn't recover in time.
"Today was unique. I've never experienced anything like that, let alone in Beijing," DeBrusk said. "It was nice to come away with two wins and gain some chemistry with the guys here. Now we're looking forward to going back to Boston."