The invention discloses a construction method for a lowering bracket of a bridge steel cofferdam. The construction method comprises the following steps that a, energization and wiring are carried out,water and electricity pipelines in a construction site are switched on, the construction site is arranged, machines and equipment, personnel allocation and materials are prepared, according to the equipment type and quantity, the appropriate primary transformer capacity is determined, according to the site layout, a plurality of secondary level distribution boxes are arranged to ensure the normaluse of a jack, water supply pipes are arranged in the ring direction of the site, and construction water is guaranteed. The construction method for the lowering bracket of the bridge steel cofferdamhas the beneficial effects that site partitioning machining manufacturing is adopted, the lowering bracket is transported onto an assembly platform at the pier position to be assembled and connected by adopting high-strength bolts, the work efficiency is improved, and the construction period is shortened, materials can be recycled in a turnover mode, meanwhile, the lowering bracket can be removedby using the buoyancy of water, diving operation is not required, the demolition turnover speed is high, and safety, economy and reliability are achieved.