Aiming at the shortcoming of adopting the Mie scattering theory to calculate non-spherical particles, the T-matrix method was used to calculate millimeter-wave extinction performance of randomly oriented cylinder particle under the conditions of different effective volume-equivalent-sphere radius, complex refractive index, and wave-length and aspect ratio. The results show that the extinction efficiency factor peak of cylinder particle enhances with the increasing of the real part of complex refractive index. With the increasing of the virtual part of complex refractive index,the extinction efficiency factor peak of cylinder particle becomes smaller, and its absorption efficiency factor rises. With the increasing of millimeter-wave wavelength, the extinction efficiency factor peak of cylinder particle remains unchanged, and the positions of peak value moves toward larger particles. The change of aspect ratio mainly influences the scattering performance, but has little impact on absorption performance. The conclusions are obtained which can provide solutions for cylinder particle to improve its extinction performance and lay the theoretical foundation to design millimeter-wave interference smokescreen.