The invention relates to a method for reducing deformation of a U-shaped composite part. The method comprises the following steps: a, making a continuous
fiber sample part according to the layer lay-up design of a target part, and measuring the U-shaped opening dimension K1 of the continuous
fiber sample part; b, making a satin fabric sample part after completely replacing the cross-ply
layers in the layer lay-up design with satin fabric, and measuring the U-shaped opening dimension K2 of the satin fabric sample part; c, calculating the layer number Q of the satin fabric after correction; and d, making a U-shaped part after correction according to the rules that the number of the cross-ply
layers of the satin fabric is Q and the number of the continuous
fiber cross-ply
layers is N-Q. According to the method for reducing deformation of the U-shaped composite part, the die surface can be obtained without long-time complicated and difficult calculation, making a new die after carrying out additional finite element calculation is not needed, and meanwhile repeated die repairing is also not needed.