Ridge waveguide apparatus will engender various distortions in use，the paper adopts the finite element method to research the influence of transmission characteristic of displacement distortion and distortion under stress to trapezoidal-ridge waveguide.Numerical results indicate that displacement distortion makes the cutoff wavelength of ridge waveguide increase，but the extent of single-mode bandwidth increased is less than 1%.For transmission characteristic of ridge waveguide，it has bigger influence and should be respected in use that distortion of ridge waveguide under stress in two sides，while deformation attains 10%，its characteristics change more than 10%.