The invention provides a PLC-based drilling combined machine tool control system. A programmable logic controller (PLC) control mode replaces a power slide hydraulic system in a relay-contactor control combined machine tool, a touch screen technology is used, a Mitsubishi PLC model is selected, design of a PLC hardware and software control system is carried out, programming is implemented on a computer by Mitsubishi programming software GX-Developer, simulative debugging is carried out by simulating software GX-Simulator, and thus, use requirements of a machine tool are ensured. By the controlsystem and a design mode thereof, working properties of reliability, convenience in maintaining and the like of the drilling combined machine tool control system are improved, and meanwhile, the design efficiency is also improved.