The paper presented here is concentrated on the subject of gain-phase margin (GM and PM) analysis in the frequency domain for perturbed vehicle control systems. The stability of a vehicle control system with perturbed parameters is analyzed by using the parameter space method and stability equations. The coefficients of a characteristic polynomial depend on some uncertain parameters. Determine whether the roots of the perturbed system are in the left-half part of the complex plane and satisfies the conditions under GM and PM constraints. These conditions can be tested graphically in 2 or 3 dimensional parameter space. The necessary and sufficient condition for stability with perturbed parameters within an operating region in the parameter space is that it contains at least one stable point and is not intersected with the image of the jw-axis in the complex plane. The proposed method is applied to an example of a bus system and simulation results are given for illustration to show the PM and GM performances.