This paper presents a pressure perturbation equation for the ultra-thin gas film lubrication of magnetic head-disk based on a generalized gas lubrication equation applicable to arbitrary Knudsen number.The gas film pressure of Air Bearing Slider (ABS) was obtained by using the operator-splitting and finite element method.The pressure perturbation equation was solved by the finite element method with unstructured triangle grids to calculate the stiffness and damping coefficients of the gas film.Modal analysis of coupled system of magnetic head and gas film was carried out to obtain natural frequencies, damping rates and mode shapes of the magnetic head vibrations.Vibration stability of Ω-type magnetic head was predicted in this work.Numerical results indicate that the natural frequencies of the coupled system increases as the gas film thickness decreases, and the natural frequencies and damping rate of the coupled vibration modes of heave and pitch motions are much lower than those of uncoupled modes.And it is concluded that the stability of magnetic head is slightly worsened when the disk rotation speed increases.