Applying cutting fluid is a common case in machining, as it can prolong the tool life. However, excessive using it may cause a bad affect on the operator and environment. Alternatively, applying minimum quantity lubrication (MQL) to reduce the bad effects yet gain a maximum advance of using cutting fluid. This study aims to determine the most optimal parameters in the AISI 4340 steel turning process with a minimum quantity lubrication method to produce the best chips formation. The best chips were measured by their possibility to break by the term degree of serration (DOS). The experiment design used was the Taguchi orthogonal array L9 〖(3〗^4). method. The varied parameters were the depth of cut, cutting speed, method of giving cutting fluid, and feed rate. Based on the mean response value, it can be concluded that to get the most optimal results of discontinuous chips would be achieved by combining parameters: depth of cut 2.2 mm, cutting speed 200 m/min, flood type cutting fluid application, and feed rate 0.107 mm/rev. Each parameter contributed to the degree of serration in order are the method to apply cutting fluid, depth of cut, cutting speed, and feed rate by 82.87%, 7.38%, 5.41% 4.14% respectively.