The objective of this study was to investigate the effects of maternal dietary energy level on indexes related in lipid metabolism of yolk and embryo serum during the middle laying period in broiler breeders. A single factorial design was adopted, and 300 AA broiler breeders (20 weeks of age) with similar body weight were randomly allocated into 3 groups with 5 replicates per group and 20 birds per replicate. The experiment was conducted when laying rate reached 5%. The birds in the control group were fed a corn-soybean meal based diet, and the others in trial groups were fed the diets with 120% and 80% energy levels of the basal diet, respectively. During the experiment period, feed intake in each group was restricted and set the same. After artificial insemination ranged from 37 to 39 weeks of age, 150 hatching eggs in each group were collected and hatched in accord with the group of the breeders during middle laying period. Yolk and serum samples were allocated at embryonic days 12, 13, 15, 17, 19 and 21. The results showed as follows: 1) in high energy group, the yolk crude fat content at embryonic days 12, 13, 17 and 19 was significantly higher than that in control group (P<0.05). The cholesterol content in high energy group at embryonic days 12, 17 and 21 and low energy group at embryonic days 13 and 17 was significantly improved compared with the control group (P<0.05). 2) The contents of low density lipoprotein at embryonic days 17 and 19, triiodothyronine at embryonic day 17, thyroxine at embryonic days 13 and 19 and growth hormone at embryonic days 15 and 17 of embryonic serum in high energy group were significantly lower than those in control group (P<0.05). However, The contents of cholesterol at embryonic days 15 and 21, glucose at embryonic days 12 and 19, low density lipoprotein at embryonic day 21, insulin like growth factor-Ⅰ at embryonic days 13, 17 and 19 in high energy group were significantly higher than those in control group (P<0.05). 3) The contents of glucose at embryonic days 12, 13, 15 and 19, low density lipoprotein at embryonic day 17, growth hormone at embryonic days 12, 17, 19 and 21 of embryonic serum in low energy group were significantly lower than those in control group (P<0.05), whereas the contents of cholesterol at examined embryonic days except for embryonic day 13, triiodothyronine at embryonic days 15 and 17 and thyroxine at embryonic day 15 were significantly higher than those in control group (P<0.05). 4) The contents of leptin throughout embryonic days and insulin at embryonic days 12, 13 and 17 were decreased with the decline of energy level in diets. The contents of triglyceride in serum throughout incubation except for embryonic days 15 and 21 were firstly reduced and then improved with the decline of energy level. The results display that maternal effect results from different maternal dietary energy levels would be observed in yolk and serum lipid metabolism with the improvements of the contents of crude fat, cholesterol in yolk and cholesterol, and triglyceride in serum during the middle laying period.