Recent progresses in research on the regularity and mechanism of sea level variations and their impacts on the offshore and coastal environment in China from 2006 to 2015 are reviewed systematically. The regularities of global and regional sea level variations and steric sea level variations on different time scales were studied, and the mechanisms of sea level variations are discussed, including the dynamic and thermodynamic effects on sea level variations in different seas due to the sea surface heat flux, freshwater flux, circulation, wind stress, and Rossby waves. The sea level variations over the 21st century were also modeled using statistical methods and numerical simulation methods. It is concluded that sea level variations have influenced ocean dynamic processes such as tidal wave changes, and further influenced the offshore and coastal environment through coastal erosion, seawater intrusion, soil salinization, estuarine saltwater intrusion, submergence of coastal lowlands, and decline of mangroves.