Milk fatty acids in milk are one of the most important factors for humans in terms of marketability and health. The composition of fatty acids has a great influence on the improvement of the functional quality of milk. The purpose of this study is to investigate each influence by estimating the genetic parameters according to the level of fatty acids in milk of Korean Holstein cows. A total of 885,249 milk test records and traits such as saturated fatty acids SFA, single unsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), and fat/protein ratios were analyzed by the CombiFoss FT+ system (Foss Analytical A/S, Denmark) analyzer. The Wombat program based on the iterative model of REML was used for genetic parameter estimation. : The composition of fatty acids showed different changes for each non-period, and also showed different energy balances(EB). With the negative EB in early lactation, mobilization of body fat reserves elevates the desirable FA levels. As a result of that, milk quality is increased by means of nutritionally and usability aspects during the early lactation. Moreover, heritability estimates for TUFA, SFA, MUFA and PUFA were 0.41, 0.33, 0.42 and 0.37 respectively. In the case of Herbidity of each industry and industry, the SFA was (0.19) in the case of 1 parity, and the level was (0.28) or more in the case of Other parity. It seems that Milk fatty acid is a very important factor in the growth of cows. Genetic parameters indicated that FAs were under stronger genetic control. Therefore, we suggest implementing animal breeding programs towards improving the milk FA profile