The invention relates to a drawing automatic pen selection device and a connection control method thereof, and the method comprises the steps that 1) a main control system sends an instruction, and the instruction is transmitted to a PLC through a 232 bus; (2) the PLC receives an instruction, a specified electromagnet is powered on, an iron core of the corresponding electromagnet extends downwards, a guide column is pushed to move downwards, a corresponding painting brush also moves downwards along with the guide column, and then the painting brush starts to work; and (3) after the paintbrushfinishes working, the main control system sends an instruction to the PLC through the 232 bus, the corresponding electromagnet is powered off, the corresponding electromagnet iron core moves upwards,the corresponding guide column resets under the action of the spring, and the paintbrush resets. The drawing equipment has the beneficial effects that the electromagnet is in threaded connection withthe fixing plate, the guide column is in threaded connection with the clamping plate, a single drawing pen is fixed through screws, disassembly is convenient, use is easy, and the process range of thedrawing equipment is effectively widened; 24-color independent paintbrushes are arranged, a 232 serial port communication mode is adopted, a control system instruction is responded, and therefore switching of the paintbrushes of different colors is achieved, and pattern drawing is completed.