Abstract: To solve the problems of low tannin acid yield, solvent residue and so on, single factor experiment and orthogonal array design were used to optimize irradiation dosage, extraction temperature, extraction time, and solid-liquid ratio parameters for the extraction of tannic acid by using the material of gallnut. The results showed that the order of the influence on irradiation pretreatment assisted extraction of gallnut tannic acid was: extraction temperature＞ irradiation dose＞ extraction time＞ solid- liquid ratio, and the extraction temperature had significant influence. The optimal process parameters for maximum tannic acid yield were determined as follows: irradiation dose was 800 kGy, extraction temperature was 90℃, solid-liquid ratio was 1: 35, extraction time was 4.5 h. The yield of tannic acid under this parameter condition could reach 65.13%, with a purity of 81.36%. Compared with that of conventional water extraction and solvent extraction, the tannic acid yield was improved by 15.13% and 20.13%, respectively.