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Flocculating yeast strains with good fermentation ability are desirable for fuel ethanol production. The flocculation ability of Saccharomyces cerevisiae NCYC 1195 is known to be affected by the concentration of calcium chloride (CaCl2) and pH. Since the calcium ion activate flocculent by forming a bond with mannose in the cell-s surface. This flocculation ability is needed to avoid the cell mixed with the fermentation medium. It will settle down the cell in the vessel, thus, there will need no centrifugation in the purification step. By doing so, the bioethanol production process will be easier, more efficient and cheaper. The aim of this study was to investigate the effect of calcium chloride (CaCl2) and pH on the flocculation ability of S. cerevisiae. This research was conducted by using three levels of CaCl2 concentration (10-5, 10-7, 10-9 M) and three level of pH (4, 5, 6). The cultures were incubated in water bath shaker at 30°C with agitation (100 rpm). The flocculation assay was conducted every 4 hours during 24 hours and the stability of flocculation was observed every 24 hours within 30 days. The highest flocculation ability was obtained (73.155%) with CaCl2 concentration of 10-9M and pH 5.