To compare the quality of cultivated Chinese yam (Dioscorea polystachya Turcz.) from Yunnan (Kunming yam) and Henan (Tiegum yam) by determining the content of dry substance in fresh sample and the contents of water extracts, ethanol extracts, starch, protein, crude-fat and polysaccharide in dry sample.The above-mentioned indexes were determined by methods of air desiccation, cold-immersing, hot-immersing, iodine-blue coloration, half Micro-Kjeldahl, Soxhlet extraction and spectrophotometric method respectively.In fresh sample, the content of dry substance of Kunming yam is a little lower than Tiegun yam; in dry sample, all indexes of Kunming yam are higher than or approach to those of Tiegun yam except the content of crude-fat. Especially the content of polysaccharide in Kunming yam is 64% higher than that of Tiegun yam.Kunming yam, with high quality, high yield and good taste, deserves paying close attention as a good variety.