We studied the effects of fish oil supplementation with low does on the lipid concentration and fatty acid of plasma and the fatty acid composition of plasma phospholipid and erythrocyte of lactating women. The subjects, 18 lactating women, who were exclusively breast-fed their babies were classifed into a control group and 2 fish oil groups according to dose; the subjects of fish oil groups were supplemented with 1.96g/d or 3.92g/d of fish oil, respectively for 2 weeks from 10 to 12 weeks postpartum. All subjects consumed their usual diet at home. Blood sample were collected at the final day of experiment. The plasma HDL-cholesterol level increased significantly by fish oil supplementation. The concentrations of DHA (docesahexaenoic acid) and EPA (eicosapentaenoic acid) in the plasma PC(phosphatidylcholine) and PE (phosphatidylethanolamine)of fish oil groups tended to increase, but not significant. However, the concentrations of DHA and EPA of PC and PE in erythrocyte were not affected by fish oil supplementation. These results demonstrate that fish oil supplementation with low dose does not change the concentration of plasma lipid as well as fatty acid composition in plasma PC and PE and red blood cell obviously. However the increase of plasma HDL-cholesterol level, the reduction of atherogenic index(AI) and the tendency of increase of DHA and EPA concentrations in plasma PC and PE indicate that there may be some beneficial effects on maternal lipid metabolism if fish oil intakes were increased.