A three mode resonance antenna with stable radiation pattern is designed using characteristic mode analysis. The antenna is composed of two layers of substrate, the upper and lower metal surfaces of upper substrate are used to form substrate integrated waveguide cavity-backed slot antenna (SIW-CBSA) which constitutes microstrip patch. And the mode TM01 of patch and modes TE110, TE120 of SIW-CBSA have basically consistent radiation pattern performance based on characteristic mode analysis. The coplanar waveguide is applied to excite modes TE110 and TE120, which connects microstrip feedline with double-layer substrate thus excite mode TM01 of patch simultaneously. Simulation results show that impedance bandwidth better than -10dB is from 8.32 to 8.77GHz, and the radiation pattern is basically consistent in whole bandwidth. Prototype size of the scheme is 1.13λ 0 × 0.79λ 0 × 0.03λ 0 (wavelength in free space).