The chip outflow angle is an important parameter for predicting the flow direction of chips in cutting, and it has guiding significance for chip control. Based on the DEFORM-3D finite element simulation software, a cutting simulation model for rounded corner cutting tools was established. The influence of tool pose, cutting depth, feed rate, cutting speed, and workpiece material parameters on chip outflow angle was systematically studied. The research results show that when the tool rotates around the X and Z axes, the chip outflow angle gradually decreases with increasing rotation angle, while the chip outflow angle remains basically unchanged when rotating around the Y axis. As the cutting depth increases, the initial chip outflow angle will continue to increase. When the cutting depth exceeds the tool fillet radius, the edge effect disappears and the tip angle remains unchanged. The chip outflow angle gradually tends to a stable value. As the feed rate increases, the chip outflow angle will gradually decrease. As the cutting speed increases, the chip outflow angle will gradually increase. The stronger the plasticity of the workpiece material, the greater the chip outflow angle. By comparing the maximum deviation values of the chip outflow angle, it can be seen that the cutting depth has the greatest impact on the chip outflow angle when cutting with rounded corner tools, with a deviation value of 29.91°. The other factors that affect the chip outflow angle in descending order are cutting speed, tool rotation around the X-axis, tool rotation around the Z-axis, feed rate, tool rotation around the Y-axis, and workpiece material.