The electric explosion wire automatic spraying device produces strong electromagnetic field during operation,which leads to the poor reliability of automatic wirefeeding system in the automatic spraying device.In order to solve this problem,an automatic wirefeeding system using Modbus communication protocol was designed to improve the reliability and stability of the automatic wirefeeding system.RS485 and RS485-to-RS232 interfaces were respectively used on the master and slave devices of the automatic wirefeeding system and they were connected by the shielded twisted pair cable.Modbus RTU transmission mode was used to transmit differential signals to improve the antiinterference ability of the data in the strong electromagnetic field.The results show that the longdistance data transmission between the master and slave devices is stable and the device runs reliably.