Although molecular simulations are useful tool for material design, it is not straightforward to apply the technique to polymeric materials due to the long relaxation time. The widely used strategy to overcome this difficulty is ‘coarse-graining’ where a set of slow variables is chosen and the other state variables are statistically embedded into the time evolution of the chosen variables. However, there has not been any established method in this coarse-graining procedure, and thus, semi-empirical models have been proposed for each specific problem. This review showcases such models to clarify the position of each model in the context of the coarse-graining.