This study was to investigate the effects of lard as main dietary energy source along with metformin supplementation on lipid metabolism and production performance of laying hens. A total of 72 brown-shell Roman laying hens with the age of 30-week were randomly assigned to 3 dietary groups. Each group had 8 replicates with 3 hens each. Experimental groups were as follows: control group (corn-soybean meal diet), lard group (soybean isolated protein-lard diet) and lard+metformin group (soybean isolated protein-lard diet plus metformin). All layers consumed the same amount of nutrients per day. Metformin was fed at 0.55 g per day per hen. The experiment lasted for 8 weeks. Results showed as follows: compared with the control group, laying rate in lard group and lard+metformin group was significantly decreased by 51.5% (P<0.01) and 59.9% (P<0.01), respectively; liver fat level in lard group was significantly increased (P<0.05) while metformin supplementation had no effects on liver fat level (P>0.05); plasma apolipoprotein B and very low density lipoprotein contents and ovary oocyte vitellogenesis receptor expression level in lard+metformin group were significantly decreased (P<0.05); yolk crude fat (P<0.01) and triglyceride (P<0.05) contents in lard+metformin group were significantly decreased; yolk oleic acid content in lard group was significantly increased (P<0.01), however, yolk linoleic acid content in lard group was significantly decreased (P<0.01). In conclusion, 1) lard supplementation can aggravate fatty liver formation and depress production performance for laying hens; 2) lard supplementation can alter lipid composition of yolk and decrease unsaturated fatty acid content; 3) metformin supplementation can not alleviate the negative effects of over-lipid deposition, but can decrease yolk total cholesterol content. ［Chinese Journal of Animal Nutrition, 2010，22（5）:1382-1389］