Abstract: In this essay, we firstly introduce the backgroundand basic conception of granular flow researches. Then we summarize three basic mathematical-mechanical models of granular flow dynamics: kinetic theory model, friction-plasticity model and discrete element simulation model. We give the basic ideas of these models and briefly analyze the merits, shortcomings and applications of each model. Then we review some prevailing experimental and measuring methods for granular flows and some typical phenomena of granular flows. In the conclusion we sketch the main difficulties of granular flow researches and put forward some topics for further studies.