Mechanics and stiffness parameters of axle box positioning device had a decisive influence on the high-speed running stability, curve passing performance and safety of rail vehicles. The rotary axle box positioning device was widely used in EMU, railway passenger cars and various types of urban rail transit vehicles. According to structural characteristics, the rotary arm type axle box positioning device was divided into four basic forms: four-body type, three-body type, two-body type and one-piece type. The technical characteristics of various structures were compared and analyzed. It was pointed out that the two-body rotary arm type axle box structure of CRH,3, EMU was optimized comprehensively, and the influence law of its positioning stiffness on the dynamic performance of each direction was provided.