Abstract: It is reported in the paper the study on the changes of IAA oxidase and peroxidase activities in Nongken 58s and control Nongken 58, during their panicle development under 14-hours sunshine a day (long day, LD)and 10-hours sunshine a day (short day SD). The results are as follows: The IAA oxidase activity in leaf of 58s LD is much lower than that of 58s SD from the formation stage of pollen mother cell to the filling stage of pollen, this makes the free IAA accumulated in leaf of 58s LD and maybe affect the pollen fertility; however, the peroxidase activity in leaf of 58s LD is much higer than that of 58s SD during the same panicle development periods, and this has nothing to do with the accumulation of free IAA in leaf of 58s LD, its effect is not known. The activities of two enzymes in panicle and anther of 58s LD are higer than those of 58s SD at the stage of meiotic division of pollen mother cell and the filling stage of pollen, this has some thing to do with the destruction of free IAA in panicle and anther of 58s LD, they may affect the fertility of 58s to a certain extent. The phenomena above have not been observed for two enzymes in leaf, panicle and anther of control Nongken 58.