Abstract: Using NMC reanalyzed ocean dataset in 1982~1993, the interannual and seasonal variations of upper level (0~400 m) in the equatorial Pacific (10oS~10oN) are analyzed. The analyses suggest the interannual variation of upper level temperature is larger than that of seasonal variation. In El Nino or La Nina year, the temperature anomalies near thermocline are more significant than those in sea surface since the depth of thermocline changes rapidly. The temperature anomalies near thermocline both in western warm pool and eastern cold tong can reach 7oC or above. In the warm pool the extreme anomalies are often in both side of the equator (4o~9o).