Abstract: Four midlate lactation Wendeng goats equipped with permanent ruminal fistulae and temporary carotid and mammary vein catheters were assigned into a 4×4 Latin square experiment. The four volatile fatty acid mixtures (VFAs) were ruminally infused with different acetate/propionate/butyrate molar ratios (75∶15∶10,VFA1; 65∶25∶10,VFA2; 55∶35∶10,VFA3; 45∶45∶10,VFA4). The food each day was delivered equally in particle by automatic feeder per 2 h and the ratios of concentrate to forage was 45∶55. Among them, the diet should meet the demand of the sheep, the VFAs infused provides of an additional 30% of MEm. The present study results showed that milk yields and milk lactose content were not influenced , but milk fat percent and yields decreased significantly by treatments (P<005). Plasma insulin increased insignificantly and there was no effect on blood glucose(P>005). With the propionate molar ratios increasing in the VFAs, arterial acetate，NEFA and BHBA consistency decreased significantly(P<005), arterial propionate increased（P<005）, but TG or butyrate was not changed in treatments (P>005). In the meantime, mammary uptake ratios of BHBA，NEFA，TG and butyrate were decreased（P<001）, propionate was increased（P<005）, but acetate was no effect (P>005). With increasing propionate molar ratio in the VFAs, contents of short and medium chain fatty acids in milk fat were increased (P<005), and that of long chain fatty acids was decreased significantly (P<005). There was no effect on trans10，cis12 CLA. Results of the present study implied that increased propionate molar ratio in ruminally infused VFAs could decrease milk fat content, depress the mammary uptake of NEFA, increase the contents of short and medium chain fatty acids and decrease long chain fatty acids in milk fat.