Optimal synthetic condition of barium sulfate were investigated from the viewpoint of yield and bulkiness according to a randomized complete block design proposed by G.E.P. Box and K.B. Wilson. Barium chloride and magnesium sulfate were utilized as reactants in order to prepare barium sulfate in this study. It was found that optimum temperature range of reactant solutions was $60{sim}100^{circ}C$ and the optimum concentration range of the reactant solutions was $10{sim}17.3%$ and $10{sim}20%$ respectively, on the viewpoint of yield and bulkiness. The optimum mole ratio of $BaCI_2$ to $BaSO_4$ was in the range of $1.50{sim}2.0$ and the optimum mole ratio of $BaCI_2$ to $BaSO_4$ was in the range of $1.50{sim}2.0$ and the optimum reacting time range was $15{sim}20$ minutes. The optimum drying temperature range was $110{sim}130^{circ}C$ from the viewpoint of yield, but it was $90{sim}110^{circ}C$ on the basis of bulkiness. Apparent viscosity of barium sulfate suspensions dispersed in various concentrations of Na. CMC was measured by using Brookfield synchrolectric viscometer model LVT, the relative equation, log ${eta}_{sp}=A+B.{phi}$ was examined and the equation was found to agree fairly well. 1 w/v% Na. CMC aqueous solution and 0.1 volume fraction of $BaSO_4$ powder were optimum in the preparation of $BaSO_4$ suspension showing highest viscosity at infinite shearing.