To explore the relationship between propagation generation? and agronomic characters and quality of Chinese yam and clarify the time to update basal part of stem,the first,second,third and fourth generations of Chinese yam basal part of stem were used as materials,and the emergence time,seedling rate,rhizome length,rhizome diameter,fresh weight and dry weight of single rhizome were studied with random block test.The contents of starch,soluble sugar and protein were determined by spectrophotometry,and the diosgenin and allantoin by HPLC.The results showed that rhizome length,rhizome diameter,single branch fresh weight,single branch dry weight and allantoin content all increased firstly and then decreased with the increase of propagation generations,and reached the maximum value in the third generation,which were 109.77 cm,31.58 mm,324.78 g,92.38 g,21.79 mg/g,respectively;While the protein content change was contrary to the above indexes,and the third generation was the lowest,which was152.89 mg/g.The content of soluble sugar decreased with the increase of generations,and reached the minimum in the fourth generation,which was 34.23 mg/g;the contents of starch and diosgenin were the highest in the third generation,which were 218.00 mg/g and 0.177 3 mg/g,respectively.We conclude that the third generation of Chinese yam has the best agronomic and quality characters,while the fourth generation has begun to decline. Therefore,it is necessary to update the basal part of stem regularly to en sure the yield and quality of Chinese yam.