This experiment was conducted to study the effects of dietary different daidzein levels on performance, reproductive organs development and hatchability of breeding eggs in Rugao yellow laying hens from 45 to 58 weeks of age. Two thousand four hundred and forty eight 42-week-old healthy Rugao yellow laying hens with a similar laying rate were assigned to 4 groups with 6 replicates in each group and 102 hens per replicate. The diet of the control group was a basal diet without daidzein, while the diets of experimental group were the basal diet added 50, 100 and 200 mg/kg daidzein, respectively. The pre-test period lasted for 2 weeks and the trial period lasted for 14 weeks. The results showed as follows: 1) there were no significant differences in the mortality, laying rate, average egg weight, average daily egg weight, average daily feed intake and ratio of feed to egg among the 4 groups (P>0.05). 2) At the end of week 12 in trial period, the ovary index and preovulatory follicle index of experimental groups were significantly decreased compared with those in the control group (P<0.05), while there was no significant difference in the other reproductive organs (P>0.05). 3) During weeks 13 to 14 of the trail, the hatchability of fertile eggs of the experimental groups was significantly increased compared with that in the control group (P<0.05), and the hatchability of setting eggs in 50 and 200 mg/kg daidzein groups was significantly higher than that in the control group (P<0.05), while there were no significant differences in the fertility and percentage of healthy chicks (P>0.05). In conclusion, under the conditions in the present study, dietary 50, 100 and 200 mg/kg daidzein can increase the hatchability of fertile eggs and hatchability of setting eggs, while no harmful effect is found in performance and reproductive organs development of in Rugao yellow laying hens from 45 to 56 weeks of age.