Niall McGinn scored in his seventh successive league match with Johnny Hayes, Chris Clark and Mark Reynolds adding the others for Aberdeen before Steven Thompson's late consolation.
The visitors struck on 10 minutes when a Hayes cross was blocked by David van Zanten but the Dons forward reacted brilliantly to crash home the rebound.
St Mirren responded when Jamie Langfield pushed a Thompson effort against the bar before the big striker sent a header narrowly wide of the target, with Gary Teale setting up both chances.
At the other end a fizzing drive from Josh Magennis was parried round the post by Craig Samson but the Buddies keeper was helpless when Ryan Fraser raced through on goal before laying off to McGinn (45) to double the advantage.
Marc McAusland brought out a wonderful save from Langfield after 83 minutes, but Aberdeen were always threatening on the counter-attack.
And the Dons wrapped up the game with four minutes remaining when Scott Vernon rolled the ball to Clark, who blasted a low shot home from close range.
Things got even worse for the hosts one minute later as Reynolds burst out of defence to fire a shot into the top corner.
There was still time for Thompson (88) to snatch a goal for St Mirren, but they damage had been inflicted by that stage.