Estrogen is one of the steroid hormones. Besides the genomic action mediated by its intracellular receptor on target cells, there is now increasing body of evidence indicating that estrogen also has non-genomic action. For the non-genomic action, estrogen binds to its receptor on cell membrane, subsequently rapidly activates various intracellular signaling pathways, such as PLC/Ca(2+), ERK/MAPK, cAMP-PKA, PI3K-AKT-NOS, and finally induces biological effects. The non-genomic effects of estrogen on physiologic and pathologic processes have been found in many tissues within the reproductive, nervous and cardiovascular systems and bone etc. In reproductive system, it has been demonstrated that estrogen plays important roles in follicle development, fertilization and embryo implantation, and it is involved in the genesis and development of genital tract tumors and breast cancer. In this review, we focus on the general characteristics of non-genomic action of estrogen, its main nonnuclear signaling pathways and physiological and pathological significance, especially its influences in female reproductive functions.