This experiment was conducted to investigate the effects of different types and supplemental levels of rumen⁃protected fat on performance and fatty acid composition of milk in Holstein dairy cows. Forty Holstein dairy cows in early lactation were selected and divided into 5 groups with 8 cows per group by random unit block according to parity, milk yield and days in milk. Group 1 was fed a basal diet consisting of whole corn silage, alfalfa hay and concentrate supplement. Groups 2 and 3 were supplemented with 4% and 5% rumen⁃ protected unsaturated fat in the basal diet, respectively. Groups 4 and 5 were supplemented with 4% and 5% rumen⁃protected saturated fat in the basal diet, respectively. The experiment consisted of a pre⁃feeding period of 7 days and a trial period of 60 days. The results showed as follows: 1) dry matter, non⁃fiber carbohydrates and crude protein intake in group 5 were significantly higher than those in groups 2 and 3 (P <0.05), ether ex⁃ tract intake in group 5 was significantly higher than that in other groups(P < 0. 01), neutral detergent fiber in⁃ take in groups 1 and 5 was significantly higher than that in group 3 (P < 0. 01), and was significantly higher than that in group 2(P <0.05) . 2) The 4% fat corrected milk yield in group 1 was significantly lower than that in groups 2,4 and 5 (P <0.05),the milk lactose production was significantly lower than that in groups 4 and 5 (P <0.05),the milk protein production was significantly lower than that in groups 3,4 and 5 (P < 0. 05), and the somatic cell count was significantly higher than that in groups 3,4 and 5 (P <0.05) . The milk protein rate in group 3 was significantly higher than that in groups 1 and 2 (P < 0. 01) . 3) The serum glutamic oxaloacetic transaminase activity in group 4 was significantly higher than that in groups 2 and 5 (P < 0. 01), the albumin content was significantly lower than that in other groups (P < 0. 05); the low density lipoprotein cholesterol content was significantly higher than that in group 4 (P < 0. 05); and total cholesterol content in group 5 was significantly higher than that in other groups (P < 0. 05) . 4) Total unsaturated and total monounsaturated fatty acid contents in groups 2 and 3 were significantly figher than those in group 5 (P <0.01), total saturated fatty acid contents were significantly lower than those in group 5 (P <0.05) and conjugated linoleic acid content was significantly higher than that in group 5 (P <0.05); total polyunounsaturated fatty acid content in group 5 was significantly higher than that in groups 1 and 4 (P <0.01) . To sum up, the addition of rumen⁃protected fat in dairy diet can effectively improve the milk production and milk protein rate, reduce the somatic cell count, adding rumen⁃protected unsaturated fat can significantly increase the total unsaturated fatty acid, total monoun⁃ saturated fatty acid and conjugated linoleic acid contents in milk, and effectively improve the quality of milk. The addition of 5% rumen⁃protected unsaturated fat is the best for dairy cows.