A 2D orthogonal cutting process of Ti6Al4V was simulated to study the dynamic process of serrated chip formation and to establish the relationship between the tool-chip contact length and the saw-tooth pitch. All orthogonal cut experiments were carried out using a machined Ti6Al4V titanium alloy bar with PCBN tools. The features of the chip back surface and the cross-section surface were analyzed. The factors that affect the formation of adiabatic shear band were investigated. For the same chip length, the variation of the number of adiabatic shear band with cutting speed was investigated. The tool-chip contact length and saw-tooth pitch were measured to explore both the variation trends with cutting speed and their internal relations. When the cutting speeds are over 110 m/min, the whole tool-chip contact area can be treated as sticking. The shear stress was used to represent the tool-chip interface characteristics, and the trend of shear stress with cutting speed was studied.