The present invention relates to a green alga with blood glucose reduction function, and more particularly a functional food produced by drying chlorella to achieve the effect of blood glucose reduction. The product may be in the form of health care food and/or pharmaceutical compound. The subject of the present invention is to employ the clinical trial for patients of Type II diabetes mellitus to verify the effect of green alga on prevention and/or treatment of diabetes mellitus, and also to observe if there is any harmful side effect after taking green alga.
