Reservoir area deepwater covering-layer-free weir-first pile-second construction method

The invention relates to a reservoir area deepwater covering-layer-free first-weir and second-pile construction method. The method comprises the following steps that a double-wall steel cofferdam is controlled to enter water along a gliding ramp through a post-pulling ground anchor and a mooring rope; a cofferdam positioning lifting system is installed on the four-corner positioning steel pile casings of the double-wall steel cofferdam, and pile foundation steel pile casings are constructed in the double-wall steel cofferdam; the double-wall steel cofferdam is lifted through a cofferdam positioning lifting system, and parallel connection between the pile casings is constructed; and a cofferdam drilling platform falls on the parallel connection between the pile casings, a cofferdam lowering and lifting system is erected through the pile foundation steel pile casings, the parallel connection between the pile casings is cut off after the double-wall steel cofferdam is lifted, then the double-wall steel cofferdam