Abstract: In order to study the changes of physical and chemical properties of fresh leaves of dandelion in different growth periods,the fresh leaves of dandelion were taken for 30,45,60,75 and 90 days of growth to analyze the stem length,stem width,sensory properties,total flavonoids,total phenolic acids,polysaccharides,polyphenols,vitamin C and crude fiber content.The results showed that the stem length,total flavonoids content,total polysaccharide content and crude fiber content of dandelion leaves increased significantly from 30 to 75 days,while the water content decreased significantly and tended to balance after 75 days. The width of upper and lower stems decreased significantly within 60 days(P<0.05).The content of vitamin C increased first and then decreased,and the content of vitamin C was the highest at 45 days. Polyphenols showed an increasing trend,while sensory scores showed a downward trend.The growth period of 30 days was suitable for fresh food or instant food such as dandelion tofu. When the growth period was 45 days,it was easy to squeeze juice. The growth period of 75 days was suitable for dandelion tea,dandelion powder and other health products and preservative products.In this experiment,the picking time of dandelion fresh leaves of different processed products was determined,which provided scientific theoretical basis for better development and utilization of dandelion.