The problem of levitation control system's restriction on the grade ability of EMS Maglev is analyzed. Firstly, based on the transform functions of the system and controller models, the relation between the grade climbing ability and frequency band and damp are corresponded by regulating the single-real pole to non-dominant pole. Secondly, the relation between the maximum tracking error and the moving velocity is analyzed based on the example of the circular transition curve. Finally, comparing the tolerable error, the relation between the minimum curve radius and the maximum climbing velocity is tabled at the end , which is significant to engineering.