The invention relates to a medical biological oral liquid, in particular to a medical biological blood sugar level reducing oral liquid and a preparation method thereof. The oral liquid consists of a bitter gourd extracting solution, a rhizoma polygonati extracting solution, a Chinese yam extracting solution, a rhizoma anemarrhenae extracting solution, a radix polygonati officinalis extracting solution, a radix ophiopogonis extracting solution, a radix rehmanniae extracting solution, a radices trichosanthis extracting solution, a fructus lycii extracting solution, a folium mori extracting solution, a radix puerariae extracting solution, a poria with hostwood extracting solution, a liquorice extracting solution, a platycodon grandiflorum extracting solution, a Rhodiola rosea extracting solution, a rhizoma atractylodis macrocephalae extracting solution, a burdock extracting solution, a schisandra chinensis extracting solution and deionized water. All raw materials are mutually matched, advantages are exerted and disadvantages are overcome, the oral liquid is used for treating symptoms such as weakness of the spleen and the stomach, body fatigue and weakness, dry mouth and reduced appetite, deficiency syndrome of the lung and cough caused by dryness, essence and blood deficiency, internal thermal and consumptive thirst. The oral liquid is capable of clearing heat-fire, helping produce saliva and slake thirst, diminishing swelling and discharging pus, and treating pyreticosis, polydipsia, lung heat, dry cough, internal heat and consumptive thirst, and the oral liquid particularly has a good curative effect for treating diabetes and reducing blood glucose.