The invention discloses an acrylic acid rosin-based high molecular surfactant which is prepared by copolymerizing oleophylic monomer acrylic acid rosin glycidyl methacrylate and hydrophilic monomer methylacrylic acid macrogol ester, and the main product has a structural general formula as shown in the specification, wherein the molecular weight range of the methylacrylic acid macrogol ester monomer is 200-1000. The invention further discloses a method for preparing the surfactant, which comprises the following steps: performing D-A addition on rosin and acrylic acid to prepare acrylic acid rosin; performing esterification reaction on the acrylic acid rosin and glycidyl methacrylate to generate oleophylic monomer acrylic acid rosin glycidyl methacrylate; and performing free radical polymerization reaction on oleophylic monomer acrylic acid rosin glycidyl methacrylate and hydrophilic monomer methylacrylic acid macrogol ester (200-1000) in a quantity relative ratio of different materials to obtain the high molecular surfactant. The high molecular surfactant has the range of number-average molar mass being 2282-6598, a range of critical micelle concentration being 0.008-0.01g/L and a range of surface tension being 54.8-55.5mN/m. The invention discloses application of the surfactant in dispersing agents, a carbon nano-tube is dispersed through strong hydrophobic effect and Van der Waals force, and transmission electron microscope indicates that the surfactant has good dispersing performance for the carbon nano-tube.