The visit to the University City became a finishing school for the Lancastrians as Cambridge showed them how to snap up chances.
The visitors had four opportunities of their own before the break but were unable to take advantage as the goals went in at the other end.
United had a far more solid defence however and a goalkeeper who did not make the kind of blunder which handed the home side their opener in the 17th minute.
Mark Angel hit a shot from 25 yards straight at French keeper Bertrand Bossu, who was making his debut on loan from Darlington, but despite getting both hands to the ball he allowed it to spin away over the line.
A minute later Cambridge won a penalty when Robbie Williams pulled back David Bridges, but the midfielder, who took the spot kick himself, hit the right-hand post.
Stanley had a chance to capitalise on that stroke of luck midway through the half, but Andy Proctor, typically, blasted the ball straight at the keeper.
It was as good as over for the second in the table team when Cambridge struck for more goals in the 34th and 45th minutes.
Darren Quinton finished of an excellent four-man move when he sidefooted home, then just before the break, Bridges volleyed past Bossu after Fola Onibuje headed down a free-kick.
Cambridge were content to hold what they had after the interval, dominating possession and having the luxury of bringing off three of their best players to rest them for the Bank Holiday weekend.
"I was very pleased with our attitude in the second half," said Cambridge boss Rob Newman, "We came down to earth after the goals and were very professional."
There was a scrap of consolation for outgunned Accrington when substitute Andy Mangan broke clear seven minutes from time to hit an angled drive which goalkeeper Darren Behcet got a hand to, but could not keep out.