∵x,y>0,且x+y=4,∴ 1x + 4y =( 1x + 4y )( x+y4 )= 14 (5+ yx + 4xy ≥ 14 (5+2×2)= 94 ,当且仅当y=2x= 83 时等号成立.故m≤ 94 ,即实数m的最大值为 94 .故答案为: 94