Abstract: Due to its wide wavelength coverage, multi-resolution mode, and high efficiency, wide field multi-object spectrograph become the work-horse general purpose instrument for the extremely large telescope. It's still a great challenge to build wide field multi-object spectrograph for a 30 m class telescope with sharply increasing volume and budget. With the great development of astronomy and astrophysics, new astronomical technology is essentially required. In this paper, the research progress of different wide field multi-object spectrographs is illustrated and reviewed, especially with the introduction about the recent status of conceptual design and their instrument features from three 30 m class telescope international projects. It also introduces the current effort made by the China's team to the TMT (Thirty Meter Telescope)-WFOS (Wide Field multi-Object Spectrograph).