Abstract: This paper deals with the influence of factors such as environmental illumination, rotation speed of screen, water temperature, structure of visual field and body length on the optomotor reaction of nile tilapia (Tilapia niloticus), and describes the reaction characteristics of individual, population and monoculars of the fish. The result shows that within certain range, the optomotor reaction of fish enhances with rising environmental illumination and water temperature, declines with increasing screen rotation speed and body-length. The fish reacts most effectively to black-and-white vertical stripes, less effectively to oblique stripes, and none to horizontal stripes. The reaction of optomotor intensifies with the increasing width and number of vertical stripes within certain range. There is no obvious difference in the reaction of individual and population. The reaction of monocular fish is evidently weaker than that of normal-binocular one, and the former has obvious orientation.