Goals from Goran Pandev, Gokhan Inler, Jose Callejon and Marek Hamsik ensured that the Partenopei stay on track behind Serie A leaders Roma
The Tuscany-based visitors were no match for Rafa Benitez's men and goals from Goran Pandev, Gokhan Inler, Jose Callejon and Marek Hamsik ensured all three points went the Partenopei's way.
The victory, which came on the back of defeat to Arsenal in the Champions League in midweek, leaves Napoli on 19 points in Serie A and a vastly superior goal difference to Juventus means that the Bianconeri this gameweek.
The likes of Gonzalo Higuain, Christian Maggio and Raul Albiol were unavailable for selection due to injury, but that did not stop the hosts getting off to an ideal start as Pandev punished the Amaranto on the counterattack by lashing in past Francesco Bardi within four minutes.
At the other end, Pasquale Schiattarella and Innocent Emeghara came close to pulling the game level before Pandev nearly doubled the lead - and his tally - but could not keep his effort beneath the crossbar.
On 26 minutes, however, Benitez's men were able to extend the difference to 2-0 and Livorno goalkeeper Bardi was arguably to blame, as he was unable to parry Inler's long-range effort over the woodwork.
Emeghara again went close as Livorno attempted to fashion a fightback, his volley thundering off the crossbar with Pepe Reina beaten and half-time imminent.
Usual service resumed after the break as ex-Real Madrid attacker Callejon, one of Napoli's many summer signings, added a third for the hosts, defeating Bardi with a low, deflected shot on 54 minutes.
Victory for the Naples side was an inevitability as the game wound to a close, though a brilliant save from Bardi kept Dries Merten's off the scoresheet as his fine free kick looked destined to find the back of the net.
But Napoli finally grabbed their fourth and final goal with seven minutes left on the clock, as Lorenzo Insigne saw his shot saved before playmaker Hamsik thumped in the rebound to score his fifth goal of the Serie A campaign.