In the area of maglev train system research, the suspension controllers are substituted by spring-dampers for the sake of simplification in a lot of documents. However the validity of this method and the reliability of the results have not been further analyzed. This paper analyzes the essential difference between the spring-damper and controller through the mathematical model, discusses its influence on the system performance from three factors: stability, dynamic responding characteristics and high frequency response. Based on the mid-test train of the National University of Defense Technology, a simulation is done to validate the difference between the spring-damper and controller. In conclusion，the paper demonstrates the substitution is nonequivalent.