Abstract: The earth system is composed of solid Earth, Atmosphere, Oceans and other fl uid layers. On the Earth, the atmospheric angular momentum (AAM) is produced between the Earth and the air moving on its surface due to the friction and the mountains. Early studies on AAM are mainly used to explain why the trade winds and the prevailing westerlies maintain in the atmospheric circulation, but recently scientists have paid more attention to researches on the variation of AAM, including mountains and friction torque, angular momentum and its transportation variations on seasonal, interannual, decadal and multi-time scales, and connected these variations with length of day (LOD), ENSO and other Earth, Atmosphere and Oceans activities. As a basic variable to describe the atmospheric circulation, the balance of AAM and its anomalies reflects the coupling process between solid Earth, Atmosphere and Oceans on multi-temporal and spatial scales, for example, the seasonal atmospheric mass redistribution (atmospheric pressure) and the driven atmospheric motion (zonal wind) (which means AAM changes) can cause LOD seasonal changes. From the perspective of the law of the angular momentum conservation, when the AAM increases, the angular momentum of the solid Earth inevitably decreases with the Earth's rotation speed slowing down and LOD increases, and vice versa. Therefore, the research on AAM has always been favored by meteorologists, astronomers and Earth scientists. This paper mainly summarizes the research progress about the exchange of momentum in the Earth-Atmosphere system and its balance, the AAM’s changes and its relation to the Atmosphere, Ocean activities, and Earth's rotation since the 1980s, and points out some problems existing in current researches in order to provide references for future studies.