The feasibility of the technological upgrading for FS41M15 numerical control milling machine was analyzed, then the implementation process of the transformation was expounded. The status and transformation requirements of the equipment were introduced, and the electrical control system and fault diagnosis and alarm system were redesigned. The precision and performance of the reformed machine tool can reach the user’s request, and good economic benefit is produced. The technological upgrading of old machine tool can not only save investment but also improve the performance of the machine tool.