The invention discloses a method for modifying a polyethersulfone forward osmosis membrane through ZIF-8 in-situ growth and an obtained membrane and belongs to the technical field of water treatment membranes. The method comprises the following steps: modifying a polyethersulfone based basement membrane with dopamine, so as to obtain a modified membrane; subjecting the modified membrane to a reaction in ZIF-8 mother liquor, and obtaining a continuous and dense ZIF-8 membranous layer on the surface of the membrane by using an in-situ growth method, thereby obtaining the membrane. The technicalscheme of the invention is the simplest and effective technology for modifying the polyethersulfone forward osmosis membrane through in-situ method growth, the entire process has no need of high pressure and high temperatures, an aqueous solvent is used and is non-toxic and pollution-free, and thus, the method is an environment-friendly synthesis process.