In this work, the form, high temperature center, and heat content of the Tropical Western Pacific Warm Pool were analyzed based on SST data and observations along Sections 137°E, 155°E and 165°E, and the relations of the warm pool’s area to the Southern Oscillation (SO) and to the Subtropical High over the West Pacific(SH) were studied. The results showed that the inter-annual variations of the warm pool’s form, high temperature center and heat content all related to the abnormality of the large scale air-sea system in the Tropical Western Pacific. There are close relations between the warm pool’s area and SO and the area index of SH. Although they have the same main period of 46.7 month, their variations differ in phase: the warm pool’s area variation lags 2, 3 months that of SO but leads by 3, 5 months that of the area index of SH.