In this article, information source characteristic degree, information sink characteristic degree and transfer equilibrium characteristic degree are defined based on transfer entropy. According to the definition, the information transfer in air-sea interaction is examined with sea surface temperature (SST) and geopotential height (GH). And the information transfer between central and eastern equatorial Pacific (20°S–20°N, 170°E–100°W) and tropics (20°S–20°N), and that between atmospheres in high latitude regions of northern hemisphere (north of 20°N) and southern hemisphere (south of 20°S) are analyzed too. In addition, decadal changes and seasonal differences in information transfer between central and eastern equatorial Pacific ocean and atmosphere are discussed by the defined indices of SST and HG. In a word, the information source distribution of ocean is mainly in tropics and the information sink distribution of atmosphere is mainly in mid-latitude. From the low-latitude to the mid-latitude, the ocean forcing the atmosphere is weakened while the atmosphere forcing the ocean is strengthened. Significant regional difference, decadal change and seasonal difference exist in information transfer from the tropical ocean to the atmosphere.