CNC vertical lathe is the main on products. The domestic and foreign demand is also very big. The key part of the high precision is on the control of the spindle. This design is with the German SIEMENS company programmable controller (PLC), S7-200 as the main controller; Germany SIEMENS company 6 ra7075 dc speed regulator, Z4 dc speed regulating device of dc motor, dc speed control was adopted to realize efficient and accurate control of machine tool spindle, and the electrical principle diagram is given.