Abstract: The laboratory flotation machine is low in operating efficiency and its products fluctuate in quality because of high impeller speed, causing the test result to be low in accuracy. To tackle these problems, numerical simulation is made of the internal flow field of the laboratory flotation machine using Fluent to explore the flow field-related problems from the aspects of velocity field and turbulence intensity. Meanwhile, a study is made on optimization of the structure of the machine. Study result shows that fitting a flow stabilizing mechanism on top part of impeller can lead to optimization of flow regime of pulp. As evidenced by comparison of test results before and after fitting the flow stabilizer, the flow stabilizer can help form a stable upward current in the separation zone, which can meet the requirement for increase of impeller speed, and reduce the adverse effect on ash content of concentrate produced by entrained fine slime. Through the optimization work, the ash of flotation concentrate is reduced by 1~2 percentage points and the ash of tailings remains basically unchanged.