A method for the calculation of optical modes in quadrupolar-shaped resonant cavities,is presented. The eigenvalue equation for resonant wavelength and optical field distribution is established. Numerical calculations are carried out for some deformation factor quadrupolar-shaped microlases. The theoretical analyses and numerical results show that the optical modes in quadrupolar-shaped microlases is typical for bow-tie mode with highly directional emission at a far-field angle Φ=45°,135°,225°,315°. This method can apply to other arbitrary cross section electromagnetic scattering and transmitting problems.