We present a semi-classical model for studying the optical responses of nano-structures, where the wave propagation is determined classically through Maxwell's equations and the motion of the nano-structure is determined quantum mechanically through Schrodinger equation. Ehrenfest molecular dynamics and Density Functional Theories are applied to deal with the many-body Schrodinger equation. The semi-classical model is numerically traceable. Linear response formulations will be derived and multi-scale solvers will be designed to solve the model. Numerical examples will be presented to demonstrate the model. (joint work with Gang Bao and Di Liu)