In this review, several capillary electrophoresis - mass spectrometry (CE-MS) interfaces based upon electrospray ionization (ESI) are illustrated. The merits, limitations and improvements of these interfaces were compared and discussed in this report. Because the CE-MS interface is most commonly based on ESI, the principle and ionization mechanisms of ESI are also introduced. Several examples were introduced to demonstrate the potential of CE-MS in the areas of environmental, biochemical and medical analysis.