This invention relates to an improved process for preparing water extract of cinnamon in a large scale. The process comprises the steps of: (a) adding an aqueous solvent such as water to at least 5 kg of a cinnamon raw material at a water to material ratio of 1:1 to 100:1, (b) boiling the mixture of (a) for at least 5 minutes, (c) removing the solid debris from the mixture, (d) storing the liquid portion of the mixture at about −5 to 25° C., preferably 0-10° C., until a top layer of oil is formed and partitioned, (e) removing the top layer of oil, and (f) collecting the remaining liquid portion. The present process prepares a cinnamon water extract product with a minimal content of potentially toxic cinnamaldehyde and coumarin, while increasing the contents of the active ingredients of polyphenolic polymers for controlling blood glucose level.