C-shaped part is one of the common parts in aviation composite structures. The cure-induced deformation when manufacturing will seriously affect the assembly of aviation structures. In this paper, a method of reducing curing deformation by applying prestressing is proposed for C-shaped part structure, and a numerical analysis model for predicting curing deformation of C-shaped part structure is established. To verify this model, three kinds of C-shaped parts of different layup sequence is manufactured at varying to prestress levels. The experimental results and numerical results have a good agreement, showing the accuracy and validity of this finite element model. It has been shown by the results that once the proper prestress is loaded, the deformation of these three layup sequence parts could reduced over 90%.