Jordy Hiwula fired past Brian Jensen to open the scoring before doubling the lead with a curling second-half strike.
Kieron Morris powered in a third for the home side two minutes later, then defender Andy Taylor's shot was deflected past Jensen for the fourth.
Substitute Jordan Cook slotted in a fifth in stoppage time as Crawley dropped into the relegation zone.
Walsall's second home win in four days lifts them seven points above the final relegation spot with four games to play.
Walsall manager Dean Smith told BBC WM 95.6:
"It was an excellent performance from start to finish. Everyone involved can be pleased with their contribution. And we've scored five goals without Tom Bradshaw getting on the scoresheet.
"To score five goals at home will have put smiles on the faces of the supporters and there were some good finishes amongst them too.
"I don't know how it was only 1-0 at half-time such was our dominance, but justice has been done as we deserved to win at their place earlier in the season and came away with nothing."
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Crawley Town boss Dean Saunders told BBC Surrey:
"We are obviously disappointed and it looks like an absolute pasting but they've scored four unbelievable strikes, three of them were amazing. The defence I put out tonight, three fullbacks and Sonny Bradley and that's what's killed us really, they were just better then us."
"I've had to change the shape of the team twice to try and stem the flow and we gradually got back into the game but really we've got a left back whose never played left back for us before. I've got Lewis Young playing at right-back whose a midfielder and I've got Lanre Oyebanjo playing centre back. We are struggling for defenders."
"I'm hoping Darren Ward is going to be fit for the weekend but we've lost Richard Wood and Dean Leacock as well. We've lost four centre halves in three months and it's caught up with us."
Walsall eased their relegation concerns with their best win of the season at home to League One strugglers Crawley.