The most of fish species have the schooling behavior, due to the different causes and mechanism of schooling, which are presented by varied definitions of different words, such as shoal, cluster or aggregation, even swam or flock, etc. This article describes and analyses the definitions and classification based on their characteristics, and recommends the word “schooling” is mostly reflecting the phenomenon of fish migration in group. The way to explore the mechanism of schooling, the factors having impact on their behavior, and the methods used in the varied studies are reviewed. And the characteristics of the structure of fish school, sub groups, the phenomena of self organization, etc. are summarized. It is recommended that the mathematics model and simulation technique are effective methods to explore the mechanism of fish self organization phenomenon. This is a way to understand nature by “linkage by phenomena only”, based on observation data, experience and phenomena observed, building mathematics model for predicating and forecasting the fish behavior and schooling structure, and the results of simulation will again be compared with the actual observation records. It might speculate or determine the dominant factors affecting the schooling phenomenon or mechanism. Meanwhile, computer technology provides support for the creation of complex models using simulation technology as an effective tool to study fish schooling behavior in recent years.