The invention relates to a linen-like type differential shrinkage composite filament and a preparation method thereof. The linen-like type differential shrinkage composite filament is a composite filament prepared from modified
polyester POY filaments and modified
polyester FDY filaments which are subjected to
fiber mixing
processing; the breakage elongation of the linen-like type differential shrinkage composite filament is 40.0+ / -3.0%, the network degree of the linen-like type differential shrinkage composite filament is 95+ / -5 piece / m; the modified
polyester consists of polyester and amino
fatty acid gylcol ester; the amino
fatty acid gylcol ester is dispersed among the molecular chains of the polyester and has a
hydrogen bonding function with the molecular chains of the polyester, so that the relative positions of the amino
fatty acid gylcol ester and the molecular chains of the polyester are fixed; under the condition that the temperature is 90-130 DEG C, the free volume space among the molecular chains of
fiber of the linen-like type differential shrinkage composite filament is increased by 20-30v / v%. Due to adoption of the aliphatic ester, the free volume of the polyester
fiber is increased, so that the
diffusion degree of dye is increased, and the
dyeing property of the polyester fiber is improved. The linen-like type differential shrinkage composite filament can be used in the industries such as high-class woof fabrics and clothes.