區(qū)別在于：

①意思不同

on free意思是自由的，免費的的意思，而for free只能是免費的的意思

Willy Lin has cut back on free drumsticks in the canteen of his Jiangxi clothing factory as meat and vegetables grow dear.由于肉價和菜價的不斷攀升，林威利削減了他的江西服裝廠食堂里的免費雞腿。

②說免費的通常不用on free，free通常很少與on搭配，for free是固定搭配

Children lining up for free food.

孩子們排隊領取免費食物。