Belanger blasted a slap shot past Ducks goalie Jean-Sebastien Giguere from in close and Mathieu Garon then shutdown Stanislav Chistov to give the Kings the win.
Anze Kopitar, Kevin Dallman, Tom Kostopoulos and Michael Cammalleri scored for Los Angeles (3-1-0) in regulation. Andy McDonald had two goals and Teemu Selanne and rookie center Tim Brent also scored for Anaheim (2-2-2).
The Kings trailed 3-0 in the second period but received power-play goals from Kopitar and Dallman.
Kostopoulos tied it 6:01 into the third and Cammalleri briefly gave the Kings a 4-3 lead with 10:41 to play before McDonald drew Anaheim even 2:24 later with his second power-play goal.
McDonald netted his first of the game eleven minutes after the opening faceoff to give the Ducks a 1-0 lead.
Brent had his fourth goal of the preseason in his fourth game and Selanne also scored on the power play to put Anaheim ahead 3-0.
Kopitar, the Kings top pick in the 2005 draft, scored their first goal during a power play at 17:45 of the second. Dallman blasted a slap shot past Giguere 48 seconds later, his third goal of the preseason.