Arranging method of channel steel cofferdam with cross section flow compensating function

The invention discloses an arranging method of a channel steel cofferdam with a cross section flow compensating function. The arranging method comprises the following steps: 1, making the steel cofferdam, wherein the steel cofferdam comprises a cofferdam body formed by an inverted U-shaped section and a blocking unit hermetically connected to the lower end part of the inverted U-shaped section; 2, mounting the steel cofferdam, to be specific, firstly, paving steel sliding rails at the two sides of a channel slope needing to be repaired in the slope direction, lifting the steel cofferdam onto the steel sliding rails, and after a locating device of the inverted U-shaped cofferdam unit slides in place along the steel sliding rails, hermetically absorbing the steel cofferdam to the upper surface of a lining plate of the channel slope through a sealing device, a sinking and floating device and an absorbing device of the inverted U-shaped cofferdam unit; and 3, arranging a flow increasing device, wherein the flow i