The optimization calculations are made to find the optimum properties of combined quadrupole lens which consists of electrostatic and magnetic lens. The optical properties are computed, where both the focal length and the magnification are determined. Both chromatic and spherical aberration coefficients are reduced to minimum values and the achromatic aberration are found for many cases. This calculation are achieved with the aid of transfer matrices method and using both rectangular and bell-shaped models of field distribution, where the path of charged-particles beam transversing the field has been determined by solving the trajectory equation of motion and then the optical properties for lens have been computed with the aid of the beam trajectory along the lens axis. The computations have been concentrated on determined the focal length, magnification and chromatic and spherical aberration coefficients in both convergence and divergence planes and also, the effects of changing both of excitation and effective length of lens are studied and are taken into account.