Accuracy management of products is one of the most important issues in industries. There are two significant ways for accuracy management. One way is accuracy control by measuring products in assembling stage. The other way is “accuracy planning” that is accuracy management in production design stage. Authors have already reported about the former, and the latter is discussed in this paper. Authors have been engaged in development of SODAS for shipbuilding CIM. Therefore authors developed accuracy planning system considered weld deformation based on SODAS. For accuracy planning, it is important to estimate deformation. Authors practice modeling of weld deformation of products and make it possible to estimate easily welding deformation. By using them, the accuracy management system by estimating of weld deformations is implemented.