The component distribution in Si-Ge bulk crystals grown by the zone leveling technique has been analyzed theoretically, with a view to estimating the operational parameters for preparing mixed crystals with the desired uniform and/or graded composition profiles. A numerical model, using the equilibrium distribution coefficient defined in the phase diagram, capable of predicting the component redistribution in Si-Ge crystal at any stage of the zone leveling growth, is proposed. Compositional profiles of Si-Ge crystals with a variety of operational parameters, such as the molten zone length and the initial ingot composition, are calculated and discussed. It was found that the Si concentration profile in Si-Ge crystal as a function of zone length changes considerably from fully graded to almost uniform along the growth direction. Obtained results allow the operational parameters for preparing Si-Ge mixed crystal to be estimated.