The effect of rare-earth Eu 3+ and Tb 3+ ions on the optoelectrical parameters of lithium sulfate monohydrate (LSMH) crystals grown by slow evaporation solution growth technique was observed. The information extracted from transmittance and re ectance spectra proved helpful in determining refractive index, extinction coe cient and various other parameters for these crystals. The effect on the volume/surface energy loss functions, optical energy gap, band tail width and tangent loss factor due to doping in these crystals were discussed. The impact of rare-earth ions on dispersion parameters derived from Wemple-DiDomeenico single oscillator model, Cauchy dispersion relation and on optoelectrical parameters derived from Drude theory was also studied. The other different parameters like optical conductivity, electronic polarizability, nonlinear refractive index, optical electronegativity, nonlinear optical susceptibility, optical and chemical hardness also get affected by doping of rare-earth ions. The relation between group and phase velocity in terms of group index in these crystals was also discussed. However, some empirical and semi-empirical rules have been used to calculate the value of the refractive index.