Abstract: Steaming is the key processing of Polygonatum kingianum. The influence of different processing time on color, soluble substance and sugar contents in Polygonatum kingianum had been studied. Changes of sugar contents with vitro simulated gastrointestinal tract environment had been investigated. The results showed that the color darkened with increase of steaming time. The soluble components of 80% vol ethanol increased significantly to 70.79% after 24 h steaming (p<0.01), while the water soluble components decreased significantly to 9.52% (p<0.01). There was no starch in Polygonatum kingianum. The content of glucose and reducing sugar increased to 4% and 47.84% after 48 h steaming, the changes were very significant. The content of crude polysaccharides in 24 h lowered and reached 9.73%. In succession steamed 24 h, the content of crude polysaccharides lowered and reached 4.26%, the change was very significant (p<0.01). There was no significant change in the content of glucose and crude polysaccharides before and after simulated gastrointestinal tract (p>0.05), but significant change in reducing sugar (p<0.05). Polygonatum flavum with high crude polysaccharide content and low glucose content should be steamed for less than 12 h. Polygonatum flavum with high reducing sugar and soluble components should be steamed for 24~48 h.