Electric closed loop multidrive NC servo control system was designed based on LabVIEW. A Siemens S120 variable frequency drive module and a electric closed loop power feedback system on one DC generatrix were used, so S7-300 PLC could exchange data with S120 through Profibus bus.At the same time,speed/torque signals were collected by PLC for PID closed loop control.Then S120 inverter module was controlled by PLC output,toachieve the goal of accurate control on speed/torque. High speed serial module communicated with LabVIEW system host computer for date exchange.The test system runs successfully, and the control feasibility of the system is verified.Utilization of power is more effectively by using electric closed loop feedback, and it has certain significance to driving control system test.