A method for generating a group key are provided in the field of network communications. The method includes the following steps: Group members select DH secret values and generate DH public values. An organizer generates an intermediate message and broadcasts a DH public value and the intermediate message. The group members generate a group key according to a DH secret value selected by the organizer and DH public values of the other group members except the organizer. A system for generating a group key and communication devices are also disclosed in the present invention.