Abstract: In order to explore the mechanism of photoperiod affecting poultry production performance, this paper investigated the changes of melatonin receptor gene expression in the hypothalamus of broilers by changing the photoperiod, and then determined the pathway of photoperiod affecting poultry production performance. 45 healthy male broilers with similar body weight at the age of 0 days were randomly divided into three groups: 8 h（L）:16 h（D） light group, 12 h（L）:12 h（D） light group, 16 h（L）:8 h（D） light group. Broilers in each group were free to eat and drink and fed at corresponding photoperied. At 14 days of age, broilers in each group were killed by decapitating and hypothalamus tissue was collected. The cDNA was obtained by reverse transcription from hypothalamus tissue. The relative expression levels of melatonin receptor Mel1 a, Mel1 b and Mel1 c gene were measured by PCR. The results showed that the expression of Mel1 a gene in 12 h（L）:12 h（D） light group decreased by 7.54%（P＞0.05） compared with that in 8 h（L）:16 h（D） light group. Compared with 12 h（L）:12 h（D） and 8 h（L）:16 h（D） light groups, the expression of Mel1 a gene in 16 h（L）:8 h（D） light group decreased by 34.32%（P＜0.05） and 39.29%（P＜0.05）, respectively. The expression of Mel1 b gene in 12 h（L）:12 h（D） light group decreased by 16.05%（P＞0.05） compared with that in 8 h（L）:16 h（D） light group. Compared with 12 h（L）:12 h（D） and 8 h（L）:16 h（D） light groups, the expression of Mel1 b gene in 16 h（L）:8 h（D） light group decreased by 22.83%（P＞0.05） and 35.22%（P＜0.05）, respectively. The expression of Mel1 c gene in 12 h（L）:12 h（D） light group decreased by 18.64%（P＜0.05） compared with that in 8 h（L）:16 h（D） light group. Compared with 12 h（L）:12 h（D） and 8 h（L）:16 h（D） light groups, the expression of Mel1 b gene in 16 h（L）:8 h（D） light group decreased by 9.40%（P＞0.05） and 26.29%（P＜0.05）, respectively. The results indicated that short light could significantly increase the gene expressions of melatonin receptor Mel1 a, Mel1 b and Mel1 c.