Preston made it 1-0 after 13 minutes with a penalty after a long ball by Paul McKenna found Richard Cresswell on the right of the penalty area.
James Walker tripped Cresswell for the penalty.
Graham Alexander hit the penalty right-footed into the bottom right for his 11th goal and ninth penalty of the season.
Dickson Etuhu made it 2-0 after 28 minutes when Eddie Lewis' left-wing cross found Etuhu and he swivelled to hit a left-foot shot into the net from close range.
Walsall made a double substitution after an hour withdrawing Steve Corica and Vinnie Samways for loan players Carl Robinson and Chris Shuker.
It was 3-0 to Preston after 63 minutes when Lee Cartwright's right-wing cross led to a Matt Carbon mistake and Cresswell hit a right-foot shot into the net for his 14th league goal of the season.
Walsall hit the bar after 72 minutes when Jorge Leitao hit a right-foot shot over Lucas but it was 4-0 to Preston in the 73rd minute when Cresswell had a shot saved and George Koumantarakis followed in to score from just two yards out.
Walsall took off Leitao for David Zdrillic with ten minutes to go.
It was 5-0 after 84 minutes when Alexander's right-wing corner was headed into the bottom right from close range by Koumantarakis.
Preston moved into 11th place in the Nationwide Division One table and they have now won four of their last five home games and six of their last eight league games.
The draw specialist tag has now gone with only one draw since November.