By using L9 (3³ ) orthogonal experimental design, effects of type, mass concentration and soaking time of phytohormones on seed germination of Carya illinoinensis (Wangenh.) K. Koch were studied, and changes in SOD and POD activities were analyzed during its seed imbibition process. The result of orthogonal experiment shows that compared with the control, soaking seed with different mass concentrations of IAA, GA3 and 6-BA at different times can improve germination rate and decrease rot rate of seeds. In which, phytohormone mass concentration has the greatest influence on germination rate, while seed soaking time has no significant effect on it. According to the experimental results, it is preliminarily determined that suitable soaking condition for seed germination of C. illinoinensis is soaking seeds for 3 d with 200 mg·L^-1GA3 . In addition, SOD and POD activities increase obviously during seed imbibition process, in which, SOD activity appears the trend of first increasing and then decreasing, while POD activity increases continuously.