The stable range of singularly perturbed maglev system parameter was studied based on cascade PID controller. Firstly, the arithmetic and model of cascade PID control maglev system were given. Then two conditions were analyzed to ensure the stability of the system: one is the asymptotically stable condition of slow PID controller subsystem; the other is the singularly perturbed stability condition of fast current loop subsystem. So the range of the stable control parameter and the upper bound of the perturbed parameter were summarized. The conclusion shows that the requirement of inherent system parameters is strict because of the strong coupling of the current loop and PID controller. This is why it is difficult to ensure the stability of the actuarial maglev system.