The present work has been performed with the aim to optimize the existing process for the production of high purity Bismuth (99.999%). A thermo-chemical database including most of the impurities (Bi-X, X = Ag, Al, Ca, Cu, Fe, K, Li, Mg, Na, Ni, Pb, Sb, Se, Si, Sn, Te, Zn, Mn, S, Cl) has been constructed to perform different thermodynamic calculations required for the refining process. Vacuum De-Zincing, a process of removing Zn in vacuum, has been introduced in the refining steps to reduce the residual Zn in the Bi coming from the Parkes process. Thermodynamic calculations and laboratory trials in the present work showed that Zn concentration can be reduced to as low as 100 ppm at 750° C and 1 Torr vacuum. With the application of Vacuum De-Zincing process the amount of chlorine that is usually used to remove the residual Zn, can be reduced significantly.