Because of the inherent appearance similar to the natural extracellular matrix, ultrafine fibrous membranes prepared via electrospinning exhibit widespread applications, especially in the biomedical area. Extensional modifications of coaxial and emulsion electrospinning have drawn much attention in preparation of core/shell fibers for applications as tissue engineering scaffolds and controlled delivery systems for bioactive substances. Due to incorporation of multi-components in the electrospun core/shell fibers, the process of coaxial and emulsion electrospinning became more susceptible. The theories have not been fully understood. A series of investigations were carried out evaluating the systematic and processing parameters. This paper reviews advantages and potentials of electrospun core/shell fibers as well as factors influencing their formation on the basis of our research and new progress.