We perform first-principles calculations of the lattice constants,elastic constants,and optical properties for alphaand gamma-uranium based on the ultra-soft pseudopotential method.Lattice constants and equilibrium atomic volume are consistent pretty well with the experimental results.Some difference exists between our calculated elastic constants and the experimental data.Based on the satisfactory ground state electronic structure calculations,the optical conductivity,dielectric function,refractive index,and extinction coefficients are also obtained.These calculated optical properties are compared with our results and other published experimental data.