The invention provides a double-oil-cylinder down jacking system and a jacking construction method thereof. Double oil cylinders are adopted as jacking oil cylinders, the bottoms of oil cylinder barrels are fixed on a bottom frame, the heads of the oil cylinder barrels are connected with a jacking framework through additional supporting structures, and rod ends of piston rods are connected with a jacking frame. The jacking frame vertically ascends and descends between an upper guide wheel layer and a lower guide wheel layer of the jacking framework and is connected with or disconnected from a main chord of a tower body through axial movement of pin shafts. The bottom of the jacking framework is fixed on the bottom frame, and the top of the jacking framework is fixed on the ground through a cable rope. The double-oil-cylinder down jacking system is simple in structure, convenient to construct, high in safety and good in operating stability in a large stroke, one standard joint is jacked in each step, the number of step changing procedures is reduced, and efficiency is high. The step changing pin shafts are matched with step holes, and the danger that descending of the whole structure does not synchronize with descending of the jacking frame is avoided effectively. The jacking framework and the oil cylinders are all directly fixed on the bottom frame and matched with the cable rope to constitute the stable system, the structure of the system is simplified, and structure self-weight is reduced.