In this study, the numerical simulation of the curing deformation of a co-cured stiffened composite panel is implemented. The curing deformation predictions of the T800 carbon fiber/epoxy resin composite stiffened panel are in good agreement with the experimental test results, which show the predictive capacity of the proposed simulation method. Through the simulation, the influences of curing parameters including heating/cooling rate, holding time and structural size parameters including width and height of stiffener and fillet radius on the curing deformation of the stiffened panel are further analyzed. These results are expected to provide guidance for the curing deformation control of co-cured stiffened composite panels from the perspective of process design and structural design.