The trial was conducted to study the effects of supplementation of 2-hydroxy-4-(methylthio) butanoic acid isopropyl ester (HMBi) for balancing dietary Lys-Met on productive performance and blood biochemical indexes in dairy cows. Forty-five Holstein dairy cows with 2～3 embryoes in late dry period were selected and assigned randomly into A, B and C group which contained 15 dairy cows. Group A as control group was fed a basal diet during total experimental period; for balancing dietary Lys-Met, group B was fed the basal diet with HMBi supplementation started from calving (1 d post-partum), and the group C was fed the basal diet with HMBi supplementation from 15 d pre-partum. The experimental period was from 15 d pre-partum to 90 d post-partum. The results showed as follows: compared with control group, the milk yields in groups B and C were significantly increased by 3.24 and 3.97 kg/d, respectively (P<0.05). The milk fat percentage in group C was significantly higher than that in control group and group B (P<0.05), and there was no significant difference between control group and group B (P>0.05). The milk fat absolute yields in groups B and C were significantly increased by 0.14 and 0.18 kg/d (P<0.05) compared with control group, respectively. Although there was no significant difference in milk protein percentages among groups (P>0.05), the milk protein yield of groups B and C was 0.10 and 0.09 kg/d higher than that in control group (P<0.05), respectively. There was no significant difference of serum glucose among all groups at day 90 of post-partum (P>0.05). HMBi supplementation in dairy cows had no significant effects on milk urea nitrogen (MUN), blood urea nitrogen (BUN) and serum total amino acid (P>0.05); however, there was a decreasing tendency in BUN and MUN. The concentrations of serum non-esterified fatty acid (NEFA), triglyceride (TC) and total cholesterol were not significantly influenced by dietary HMBi supplementation (P>0.05), but there was a trend to decrease the NEFA and TC. The results indicated that balancing dietary Lys-Met by supplementation with HMBi could improve productive performances, and there was a tendency to improve metabolic conditions.［Chinese Journal of Animal Nutrition, 2010，22（2）:372-379］