The ab initio method has been performed to explore the elastic and optical properties of Al3Sccompound, based on a plane wave pseudopotential method. It can be seen that the calculatedequilibrium lattice parameter and elastic constants are in reasonable agreement with the previousexperimental data. The elastic constants satisfy the requirement for mechanical stability in the cubicstructure of the Al3Sc compound. The optical property calculations show that a strong absorptivepeak exists from 0-15eV and a relative small absorptive peak exists around 30eV. The form iscaused by the optical transitions between high s, p, and d bands, and the latter results from theoptical transitions from high s, p, and d bands to the low 2p band.