Abstract: A method of estimating the manufacturing cost for composite stiffened panels was proposed on the basis of co-curing process. Considering cost as a major design parameter，an approach to optimize the configuration that minimizes the cost and weight of composite stiffened panels under compression and shear was presented，under structural requirements and manufacturing const raints. Based on the case of panel with T stiffener，the objective function of cost and weight was minimized respectively to verify the cost estimation model. The results estimated are in good agreement with practical process time of lay up. In addition，the stiffened panel cost and weight were discussed for seven stiffener cross-sectional shapes. It is found that T stiffener gives the lowest time configuration while its weight is only 0.5% more than that of the J stiffener，while J is of the lowest weight among seven stiffeners. The optimization conclusion can be applied to guide design of composite stiffened panel.