The Gunners, aiming to become champions for the first time since 2003-04, went ahead at Emirates Stadium through Gabriel Martinelli’s left-footed strike.
It was his sixth goal in six league matches.
Bukayo Saka doubled the lead in the 43rd minute, finoshing off abcurling pass from Brn White.
Granit Xhaka made it 3-0 with a first-time finish from Leandro Trossard’s assist, before Jeffrey Schlupp pulled one back from close range following a corner for Palace’s first goal in five matches.
But the excellent Saka restored Arsenal’s three-goal advantage with a guided finish from Kiernan Tierney’s pull-back to seal the victory.
Arsenal have 69 points from 28 matches, with second-placed Manchester City on 61 points having played a game less