50%左右。 Moisture of extruder feed material,heating temperature of extruder barrel and rotation speed of extruder screw were considered as factors;tannin content was employed as evaluation index. With the aid of the combination design of quadratic orthogonal rotation, the regression equation was established,the single factor and response surface methodology were used to demonstrate the influential rules of test factors to the index changes,and the contribution rate of factors to the index was investigated, the extruder condition of lower tannin content was fixed by the frequency analysis. The results show that the tannin content decreases to 50% when heating temperature of extruder barrel is 50℃，rotation speed of extruder screw is 166 r/min and moisture of material is 25%. 