Solidification condition for preparing transparent ${gamma}$-6Bi2O3.GeO2 polycrystals by unidirectional solidification of melt, were investigaetd and the properties of the polycrystals prepared were measured. The ${gamma}$-6Bi2O3.GeO2 polycrystals showing transparency like a single crystal were obtained by the unidirectional solidification of ${gamma}$-6Bi2O3.GeO2 melt at a solidification rate of 0.5mm/h under a thermal gradient of 12$0^{circ}C$/cm. The transparent polycrystals obtained showed the same photoconduction and optical activity as the ${gamma}$-6Bi2O3.GeO2 single crystals grown by Czochralski method. But the electro-optic effect of polycrystals was heterogeneous because the colummar ${gamma}$-6Bi2O3.GeO2 crystals were not oriented to the particular crystallographic direction.