Some phosphate ester groups are known to link to glucosidic residues in starch molecule. We have prepared phosphoryl oligosaccharides (POs) from potato starch hydrolysates. POs were composed of two fractions, PO-1 and PO-2. The PO-1 fraction was the main fraction, and it was composed of maltotriose, maltotetraose, and maltopentaose to which one phosphoryl group was attached. The PO-2 fraction was predominantly composed of maltopentaose and maltohexaose to which at least two phosphoryl groups were attached. POs had the ability to form a soluble complex with calcium. Based on the function of the POs, we developed the POs of calcium (POs-Ca) for a food ingredient. POs-Ca was an advantageous food ingredient as a soluble calcium source and relatively high absorption in the intestinal tract. Relating to prevent of dental caries, POs cannot be fermented by cariogenic microorganisms, mutans streptococci, and reduces the plaque pH fall in vitro by mutans streptococci. Moreover, POs-Ca was effectively enhanced remineralization of early caries lesion. Although relatively higher pH in stimulated saliva is not suitable for Ca and phosphate (P) to be solubilized, POs-Ca would aid to maintain their solubility in oral environment. In results, the salivary Ca/P ratio can increase nearly up to the rate of hydroxyapatite (1.67) and enhanced enamel remineralization. Thereby, POs-Ca could be a beneficial material for oral health. Abbreviations : POs, phosphoryl oligosaccharides; POs-Ca, phosphoryl oligosaccharides of calcium; Ca, calcium; P, phosphate; 6³-phosphoryl maltotriose, O-6-phosphoryl-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranosyl-(1→4)-D-glucopyranose; 6²-phosphoryl maltotriose, O-α-D-glucopyranosyl-(1→4)-O-6-phosphoryl-α-D-glucopyranosyl-(1→4)-D-glucopyranose; 6³-phosphoryl maltotetraose, O-α-D-glucopyranosyl-(1→4)-O-6-phosphoryl-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranosyl-(1→4)-D-glucopyranose; 6⁴-phosphoryl maltopentaose, O-α-D-glucopyranosyl-(1→4)-O-6-phosphoryl-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranosyl-(1→4)-D-glucopyranose; 3³-phosphoryl maltotetraose, O-α-D-glucopyranosyl-(1→4)-O-3-phosphoryl-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranosyl-(1→4)-D-glucopyranose; 3⁴-phosphoryl maltopentaose, O-α-D-glucopyranosyl-(1→4)-O-3-phosphoryl-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranosyl-(1→4)-D-glucopyranose.