G protein-coupled estrogen receptor 1 (GPER) is a novel receptor, which belongs to the family of G protein-coupled receptors, to many of the rapid biological responses to estrogen. Different from the two classical nuclear estrogen receptors, ERα and ERβ, GPER modulates both rapid non-genomic reaction and genomic transcriptional events of estrogen. In this regard, GPER may be considered as a valuable target toward novel therapeutic strategy for many estrogen-related diseases. The intrinsic appearance of GPER, including structure, subcellular localization, ligands, signal transduction pathway and relationship with diseases is reviewed in this paper.