Abstract: The micromechanics and the finite element analysis method (FEA) were used to predict the cure-induced deformation (CID) of CCF800H/AC531 carbon fiber/epoxy composite U-shaped parts with variable thickness. The effects of flange and various thickness area parameters on CID were studied by response surface methodology (RSM). The material properties of unidirectional composite were determined by self-consistent method, and the equivalent properties of laminates were calculated by FEA based micromechanical model to avoid the complex layer division and direction definition of the numerical model. The CID of U-shaped parts was predicted by the curing hardening instantaneous linear elastic model (CHILE). A case part was manufactured to verify the accuracy of the FEA. It can be found that the lay-ups and material types have no influence on the law of variable thickness area’s effect on adjacent areas. Then two plans were designed by the Box-Behnken RSM method to analyze the influence of flange parameters and variable thickness area parameters, and two quadratic regression models were fitted, respectively. The investigation reveals that the variable thickness area greatly influences the thinner area, with a maximum reduction of CID of about 15%. The variable thickness area has little effect on the thicker area. Besides, the CID is unaffected by the width of the variable thickness area. The variable thickness area has no effect on the CID of a cross section if it is 150 mm or more away from the cross section.