The boundary between science and non-science， scientists group and the public， and the relationship between such boundary and the authority of science have been hot issues in the field of sociology of science since the end of 20th century. Facing this issue， this research has chosen Zhihu as research field， and used discourse analysis as research methods to analyze the discourse features of scientists group on Zhihu and tried to investigate the ideology and boundary setting of scientists group via analyzing such discourse features. This research will provide some new perspectives for approaching the authority of science in science communication process. The findings show that the scientists on Zhihu adopted a series of ‘boundary setting’ discourse techniques in the online science communication about GMOs， which confirmed the identity boundary between themselves and the public， and thus further maintained their own discourse authority in the online science discussion and communication process.