This paper analyses some practices of maritime delimitation of coastal countries and judicial practices of the International Court or Arbitration Court after the brief introduction of the general geography and resources conditions of East China Sea. On the basis of above analysis, the author sums up some main factors considered by relevant states when they delimitate the maritime boundaries, such as geography, geology, the unity resources, economy, historical rights ( traditional fishing right) . The author analyses these factors combined with Chinese, actual conditions, then expounds the possible delimitation: delimitating the Exclusive Economic Zone (EEZ) and the Continental Shelf on respective length proportionality of coastal lines. At last, some viewpo ints are expounded about the marine boundary between China and Japan.