The invention discloses a method for improving a fast-growing wood performance through a rosinyl unsaturated resin. The method comprises the steps of adopting hydrogenated rosin and glycidyl methacrylate as raw materials, carrying out esterification reaction to prepare the rosinyl unsaturated resin, preparing into an ethanol solution with the mass concentration being 1 percent to 30 percent, adding an initiator accounting for 1 to 5 percent of part by weight of the unsaturated polyester resin, impregnating fast-growing wood for 20 to 60min under the vacuum degree being 0.08 to 0.1MPa, impregnating for 20 to 28h under the normal pressure at the room temperature (20 to 27 DEG C), filtering out, drying in a drying oven for 4 to 6h at 40 to 60 DEG C, then heating to 90 to 100 DEG C, curing for1 to 6h, curing for 1 to 8h after heating to 135 to 160 DEG C, and obtaining rosinyl unsaturated resin modified fast-growing wood. After curing, the density of the fast-growing wood is increased by 4.76 to 17.07 percent, the weight percentage increment (WPG) is 4.90 to 18.16 percent, the hardness is increased by 0.59 to 1.23 percent, and the contact angle is increased by 47.41 to 75.68 degrees.