The invention provides an oligosaccharide oat beverage capable of treating hyperlipoidemia and hyperglycemia and improving gastrointestinal tract function and a manufacturing method thereof by hydrolysis of three enzymes and fine grinding. The manufacturing method comprises the following steps: carrying out fine grinding on the oat meal to obtain the powder of which the average particle size is less than about 100 mu m, dissolving the oat powder in water to form oat slurry, and adding alpha-amylase, beta-amylase and trans-glucosidase to carry out enzyme treatment, thereby obtaining the oat beverage with rich functional components. The oligosaccharide oat beverage integrally reserves oat beta-dextran, and also contains oligo-isomaltose component of which the content is higher than that in common oat products. The manufacturing method can integrally reserve the nutritional components of the whole oat grains and omit the filter operation, thereby being beneficial to increasing the utilization ratio of raw materials; and the method is completed under the conditions of fermentation and sterilization in the optimal short time, thereby avoiding the possibility of rancidity of oat slurry in the processing procedure. When the oligosaccharide oat beverage is used for human testing for assessing physiologic effect, the test proves that the oligosaccharide oat beverage can lower the total cholesterol, low-density lipoprotein cholesterol, triglyceride and fasting blood-glucose value in blood. The oligosaccharide oat beverage tastes savoury, thick and smooth like milk, and maintains the natural flavor of oat; and thus, the invention changes the traditional way for eating oat, greatly raises the nutrition health-care value of oat processed products, and has the potentials of preventing and treating hyperlipoidemia, hyperglycemia and other life-style related diseases and improving the gastrointestinal tract function.