The sealing surface of the plug valve is that the valve body and the valve core are in contact with each other in the form of a tapered surface, and the surface roughness is not lower than Rα0.8. After the car is processed, a grinding process is performed. The grinding quality of the cone directly determines whether the plug valve leaks. According to the practice over the years, the following views are proposed on how to improve the grinding quality of the plug valve.