The invention discloses a channel improvement construction method, and relates to the engineering construction technology. The problem that due to common channel improvement construction, the water depth of a channel is increased, and the channel danger is increased is solved. The method comprises the following steps of cofferdam construction, wherein in the length direction of a channel, waterproof cofferdams are sequentially arranged in the length direction of a channel to segment the channel; channel dredging, wherein starting from the upstream of the channel, water and sludge in a dredgingsegment are sequentially discharged into the next dredging segment, and after sludge is cleaned, a river bed needs to be backfilled and reinforced; and channel recovering, wherein after the channel is cleaned and improved, the cofferdams are dismounted, and river water flowing is recovered. The method has the advantages that backfilling and reinforcing after dredging can recover the depth, descending due to dredging, of the channel, the channel can keep safe depth, through renovation, the river bed is more flat in topography, after a person falls in water, the person cannot be tangled by theriver bed complex topography easily, and the construction method can reduce danger of the channel.