NOVELTY - Simultaneous extraction of polysaccharides, flavonoids and alkaloids from Dendrobium nobile, by grinding dried stem of D.nobile, placing powder in stainless steel extraction container, subjecting the powder to subcritical water extraction, cooling extract, subjecting cooled extract to adsorption resin column chromatography, eluting the column sequentially with water and ethanol solution, removing eluents and collecting 3 eluates, concentrating eluates under reduced pressure, and vacuum-drying concentrate to obtain dried concentrate.    USE - The method is useful for simultaneous extraction of polysaccharides, flavonoids and alkaloids from D.nobile (claimed).    ADVANTAGE - The method enables simultaneous and highly efficient extraction of product containing 65-71% polysaccharides, 77-83% flavonoids and 60-65% alkaloids at rate of 90-94%, 90-92% and 86-88% respectively within short period of time, and performs separation and extraction processes together without use of toxic organic solvents, and hence is environmentally-friendly, and simple and easy to operate, and has low production costs.    DETAILED DESCRIPTION - Method for simultaneous extraction of polysaccharides, flavonoids and alkaloids from Dendrobium nobile, involves (a) taking dried stem of D.nobile, and grinding dried stem to obtain powder having particle diameter of 0.03-0.2 mm, (b) placing the powder in stainless steel extraction container, and subjecting the powder to subcritical water extraction for 20-120 minutes, (c) cooling extract to room temperature, subjecting cooled extract to adsorption resin column chromatography, eluting the column sequentially with water and ethanol solution, removing eluents and collecting 3 eluates, where firstly 0.3-2 volumes of adsorption column is eluted with deionized water, secondly 2-4 volumes of adsorption column is eluted with 20-50% ethanol solution, and thirdly 2-4 volumes of adsorption column is eluted with 90-100% ethanol solution, and (d) concentrating eluates under reduced pressure at 40-75 degrees C, and vacuum-drying concentrate at 45-60 degrees C to obtain dried concentrate, where first, second and third eluates are concentrated at 50-75 degrees C, 45-65 degrees C and 40-65 degrees C respectively to obtain product containing polysaccharides, flavonoids and alkaloids respectively.