Female migrant workers have made a significant contribution to the rapid development of China, but they are marginalized in the current social structure. This research was conducted to investigate the identity construction of female migrant workers in online groups. Virtual ethnography was the primary method used to study two online groups for nine months. Castells’s categorization of identity was adopted to examine the identity construction process. Our thematic analysis revealed three underlying mechanisms of identity construction among female migrant workers: sharing experiences to break the silence; the leading role of non-governmental organizations (NGOs); and setting boundaries to indicate identity. The results showed that although the female migrant workers internalized their legitimizing identity as a “machine,” they constructed themselves as united resistant female workers who opposed suppression, and they desired to project the identity of “decent workers.” Our findings suggest that dominant institutions should consider female migrant workers’ gender issues and work closely with NGOs to help them obtain their desired identity and social equality in urban settings.