The onset and development of ENSO events are affected by both tropical western Pacific and subtropical Pacific. This paper provided an overview of scientific background and research progress on anomalies over subtropical Pacific affecting ENSO events.It reviewed about studies of physical mechanisms of atmosphere-ocean anomalies over subtropical Pacific on ENSO through meridional wind stress and the meridional modes of the South and North Pacific, summarizing new ideas concluded from analysis and numerical simulations in recent years.Academic divisions and issues needed to study in future were also discussed.