The effect of different plasma pressures on the radial perturbed displacement with wave numbers k and growth rate γ in a cylindrical plasma column is given. The linear numerical simulation indicates that the radial perturbed displacements almost never change when the plasma wavelength is longer, that is to say, the effect of plasma pressure on a longer plasma wavelength is insignificant. The range of wave numbers k increases with an increase of the plasma pressure. Moreover, radial perturbed displacements oscillate obviously when the plasma pressure is non-uniform, which indicates that non-uniform plasma pressure has great destructiveness on the kink instability.