Objective: To compare the composition and fraction molecular weight distribution of polysaccharides from natural Cordyceps sinensis and cultured Cordyceps mycelia. Methods: A gel filtration HPLC equipped with TSK - Gel G3000SWXL column(5 μm,7. 8 mm ×30 cm)and guard column(7 μm,6. 0 mm×4 cm)were applied for a-nalysis. The mobile phase was 0. 1 mol·L-1 sodium sulfate in 10 mmol #L-1 phosphate buffer(pH 6. 8 ) and the flow rate was 1 mL·min-1. The column and detect temperature were 25℃ ,and refraction index detector was used. Results:The composition of polysaccharides from natural Cordyceps sinensis was similar. The molecular weight of main fraction( >50% ) was more than 1. 5 × 105. The polysaccharides of cultured Cordyceps mycelia of east region of China was similar to those of natural Cordyceps sinensis, though the composition of polysaccharides from cultured Cordyceps mycelia was obviously different. Conclusion: The polysaccharides of natural Cordyceps sinensis and those of cultured Cordyceps mycelia were found to be different in composition. Determination of polysaccharides should be used as quality control of natural Cordyceps sinensis and cultured Cordyceps mycelia.