A method for sending a connection establishment request is provided, comprising: sending a parameter requesting message to a configuration server from an OpenFlow switch for obtaining connection parameters of an OpenFlow controller; receiving by the OpenFlow switch an Internet Protocol (IP) address and a set of OpenFlow controller connection parameters sent from the configuration server, the set of connection parameters comprising at least connection parameters of a first OpenFlow controller; sending a connection establishment request message to the first OpenFlow controller from the OpenFlow switch according to the IP address and the connection parameter of the first OpenFlow controller. An OpenFlow switch, a configuration server and a system for sending a connection establishment request are also provided. With the solutions provided in embodiments of the disclosure, the automatic connection establishment between the OpenFlow switch and the OpenFlow controller can be realized.