An access method of a PROFINET protocol in an industrial SDN, comprising a message processing flow of the PROFINET industrial Ethernet protocol in an industrial software defined network switch, comprising the following steps: when the industrial software defined network switch receives a PROFINET-DCP broadcast message periodically transmitted by a PROFINET master station device, flow table matching is conducted, and the PROFINET-DCP broadcast message is forwarded according to a forwarding action specified in a flow table; when the industrial software defined network switch receives a PROFINET-DCP response message of the PROFINET-DCP broadcast message transmitted by a terminal device for the PROFINET master station device, flow table matching is conducted, and the PROFINET-DCP response message is forwarded according to the forwarding action specified in the flow table; according to the PROFINET-DCP message between the PROFINET master station device and the terminal device, an industrial software defined network controller establishes a logical communication link in the industrial software defined network in a way of issuing the flow table to complete the device networking access, characterized in that a networking process of an industrial Ethernet protocol master station and the terminal device is as follows: the master station sends an MAC layer broadcast message to a network port; after receiving the broadcast message sent by the master station, the terminal device replies with own status information; the master station device receives the reply from the terminal device and sets the configuration information through an MAC layer unicast message; after receiving the MAC layer unicast message, the terminal device replies to the master station device and configures a success message; after receiving the success message sent by the terminal device, the master station device initiates ARP network layer addressing and conducts address resolution; the terminal device replies with the APR network layer addressing and notifies an MAC address corresponding to an involved IP address; the master station device initiates data communication to the terminal device; the master station device and the terminal device conduct communication and data transmission. when the industrial software defined network switch receives a PROFINET-DCP broadcast message periodically transmitted by a PROFINET master station device, flow table matching is conducted, and the PROFINET-DCP broadcast message is forwarded according to a forwarding action specified in a flow table; when the industrial software defined network switch receives a PROFINET-DCP response message of the PROFINET-DCP broadcast message transmitted by a terminal device for the PROFINET master station device, flow table matching is conducted, and the PROFINET-DCP response message is forwarded according to the forwarding action specified in the flow table; according to the PROFINET-DCP message between the PROFINET master station device and the terminal device, an industrial software defined network controller establishes a logical communication link in the industrial software defined network in a way of issuing the flow table to complete the device networking access, the master station sends an MAC layer broadcast message to a network port; after receiving the broadcast message sent by the master station, the terminal device replies with own status information; the master station device receives the reply from the terminal device and sets the configuration information through an MAC layer unicast message; after receiving the MAC layer unicast message, the terminal device replies to the master station device and configures a success message; after receiving the success message sent by the terminal device, the master station device initiates ARP network layer addressing and conducts address resolution; the terminal device replies with the APR network layer addressing and notifies an MAC address corresponding to an involved IP address; the master station device initiates data communication to the terminal device; the master station device and the terminal device conduct communication and data transmission.