The Reds opened the scoring in the 14th minute when Phillipe Coutinho was brought down inside the box and a penalty was awarded. The midfielder made no mistake in dispatching his spot kick into the net.
Preston were nearly on level terms when Scott Laird tested debutant Simon Mignolet in the Liverpool goal, but the Belgian managed to beat away the 25-yard effort.
Brendan Rodgers's side doubled their lead just before half time when Jordan Ibe found space and time on the edge of the area as he used quick feet and then drilled the ball into the bottom corner.
After the break Raheem Sterling had a great chance to grab a third but his effort was well saved by Thorsten Stuckman in the home side's net.
However, Sterling wasn't to be denied minutes later as he raced clear down the pitch, rounded Stuckman and slotted the ball into the empty net in the 64th minute.
Liverpool got their fourth in spectacular fashion as Iago Aspas received the ball from Glen Johnson on the edge of the area and fired it first time into the top corner to seal the win at Deepdale.