The application provides medicinal tea for treating diabetes mellitus. The medicinal tea is prepared from fructus momordicae charantiae, radix et rhizoma ginseng, radix notoginseng, fructus mume, fructus crataegi, semen persicae, flos lonicerae, poria cocos, semen coicis, herba taraxaci, radix puerariae, folium ilicis latifoliae, pericarpium citri reticulatae, concha ostreae, rhizoma coptidis, radix scutellariae, radix et rhizoma rhei, radix trichosanthis, cortex lycii, rhizoma imperatae, radix ophiopogonis, rhizoma anemarrhenae, pericarpium granati, red yeast rice, radix paeoniae alba, radix ardisiae crenatae, herba spirodelae, fructus lycii, semen cuscutae, cortex eucommiae, fructus psoraleae, fructus schisandrae and rhizoma zingiberis recens. The natural antagonism between bitterness and sweetness is utilized; an acid neutralizes the sweetness; the bitterness and the acid lower blood sugar; the yin is nourished; the heat is cleared away; the diuresis is realized; the blood circulation is promoted; the blood stasis is dispersed; the lipid is reduced; a complication can be effectively prevented; the medicinal tea can be directly used for a diabetic for independently lowering the blood sugar, decreases the glycaemic index of a patient, and improves a clinical symptom.