Polymeric pigments and tannins are essential components in grape and wine. A common method for measuring polymeric pigments and tannins in grape and wine is using protein precipitation assay(A-H). In order to investigate the impact of sugars on tannins and polymeric pigments determined by the A-H method, the concentrations of polymeric pigments and tannins in wine samples were tested after adding different amounts of sugars (glucose, fructose and sucrose). The experiment result showed that after all the treatments the contents of non-protein-precipitable small polymeric pigments （SPP）and total polymeric pigments （TPP） were affected significantly by sugars (glucose, fructose and sucrose) in wine, and the effect of sucrose was greater than those of glucose and fructose. However, difference was found in the amount of protein-precipitable large polymeric pigments (LPP). Some of treatments by sucrose and glucose had significant impact on the concentration of LPP, but the content of LPP was affected insignificantly by fructose in wine. One possible explanation for the different impacts of sugars on polymeric pigments and tannins was that sugars could have significant influence on the combination of protein with polymeric pigments. Meanwhile, the experiment result also indicated that sugars (glucose, fructose and sucrose) can significantly decrease the content of tannins in wine. Therefore, caution needs to be exerted when using the A-H method to determine polymeric pigments and tannins in wine with high content of sugars.