Titanium alloy TC4 is widely used in aerospace and other fields due to its high strength-to-weight ratio and excellent corrosion resistance. TC4 has high chemical activity and low thermal conductivity. Unfortunately this results in low processing efficiency and poor surface quality of workpiece. In order to obtain the variation of chip morphology with cutting speed in high-speed milling titanium alloy TC4, and thus to improve the machined surface quality and cutting efficiency, the formation of the serrated chips and the characteristic of the corresponding surface topography in milling TC4 were investigated. In this paper, the finite element software was used to reasonably simplify the milling process of TC4 with YG8 carbide tools, and a two-dimensional variable-thickness cutting model was established to reduce the computational cost and facilitate the observation of microscopic chip morphology. The post-processing results of the model were combined with the TC4 milling experiment to measure the error between the simulation and experiment values of the milling force during the milling process. The effect of the milling speed on the chip morphology was obtained. With milling speedof 120 m/min as an example, the Mises stress, equivalent plastic strain and milling temperature during the three-stage formation of serrated segments were simulated and analyzed. The geometric characterization of the serrated chips was defined through the serration coefficient, the shear angle, and the shear band spacing. The relationship between the milling speed and these characterization variables was studied. Extended depth-of-field microscope and PS50 surface profiler were used to observe and analyze the chip morphology and surface topography formed during TC4 milling, and to determine the relations between the milling speed and chip morphology/workpiece surface topography/surface roughness during milling. The results showed that the maximum error between the simulation and experiment values of the milling force was 9.86%, which verified the accuracy of the 2D variable-thickness cutting model. As the milling speed increased from 40 m/min to 120 m/min, the chip morphology changed from strip to the serrated, and the milling force gradually decreased. 80 m/min was the critical milling speed for serrated chips. The simulation results showed that with the generation of serrated segments, the Mises stress at the first deformation zone gradually decreased, and the equivalent plastic strain value near the middle of the two shear bands also decreased gradually. Meanwhile, the milling temperature in the first deformation zone increased firstly and then decreased. When the milling speed increased from 80 m/min to 240 m/min, the chip serration coefficient and the shear angle both increased, while the shear band spacing decreased. Accompanied by the appearance of a large number of dimples, the surface roughness value increased. When the milling speed was 200 m/min, the increase of the surface roughness value was relatively slow, and the milling efficiency of TC4 was becoming higher. Knowing the change law of the geometric characteristics of serrated chips and surface topography of the workpiece with the milling speed so as to control the serrated chips, is of great guiding significance for improving the surface quality and machining efficiency in TC4 milling process.