<p>The influence of negative chamfer angle on the machined surface quality of WNbMoTaZr_x (x = 0.5, 1.0) refractory high entropy alloys (RHEAs) was investigated. The results showed that the increase of negative chamfer angle can improve the machined surface quality of RHEAs. Such improvement was mainly attributed to the plough press effect of the negative chamfer surface and the self-healing ability of the machined surface. With the increase of the negative chamfer angle, the shear angle decreased, resulting in the elongation of the shear slip band and the increase of cutting force. During machining, the negative chamfer surface would press the materials in the metal stagnation area onto the machined surface, resulting in a smooth machined surface. Meanwhile, the high temperature caused the workpiece surface to develop a self-healing ability, which smoothed the ridge of the ploughing groove. Finally, the machined surface quality of RHEAs had been significantly improved to Ra = 0.5&#xa0;µm. In addition, the morphology of the chip and machined surface was examined, where the machined surface was mainly characterized with plastic flow, side flow, and ploughing grooves. The chip-free surface was mainly characterized with tooth top, shear band, and burr. With the increase of negative chamfer angle, the serrated inclination angle slowly decreased because of the shear angle decrease. The main tool wear for the machining of RHEAs was adhesive wear. This work provides useful guidance for improving the machined surface quality of RHEAs.</p>