Abstract: Based on the oceanographic and meteorological data provided by the Climate Analysis Center (CAC) of National Oceanic and Atmospheric Administration (USA) and climate monitor bulletin of State Meteorological Administration (PRC), comprehensive analyses for the characteristics of genesis and evolution of 1991/1992 ENSO event are made in this paper. The results show that the main feature of this ENSO event is as follows that (1) anomalous oceanic and atmospheric characteristics frequently appear one year prior to ENSO event, which caused the warm water accumulate in the central equatorial Pacific (5°N-5°S, 160°E - 160°W) for about twelve months, before transporting from the west to the east to trigger the 1991/1992 ENSO event; (2) the anomalous variation of subtropical high in the western Pacific responding to ENSO event occurred twelve months prior to the onset of this ENSO event, and it appeared to be obviously strong, and its position to the northwest was comparable with normal condition during the onset stage of ENSO, Which results in anomalous meteorological factor occurrence prior to ENSO event; and (3) the air - sea parameters during this ENSO event appear twice anomalous variation corresponding to ENSO, and the second anomalous variation is the main reason for making the ENSO event a long and strenghened period.