lol is the English internet abbreviation, borrowed into Chinese online chat alongside native equivalents 哈哈 / 23333 / XSWL (笑死我了 'dying of laughter'). Younger Chinese bilingual users mix lol in freely; older users overwhelmingly prefer 哈哈.
usage
Warning for context: on Chinese gaming sites lol usually means the game League of Legends (《英雄联盟》), abbreviated LOL. Context distinguishes them — 'lol 好笑' = 'lol funny', 'LOL段位' = 'League of Legends rank'.