Abstract: Sound field separation technique with double holographic planes is proposed, which overcomes the limitation on applications of near-field acoustic holography (NAH) and broadband acoustic holography from intensity measurement (BAHIM). The limitation is: sound field on one side of holographic plane must be free, that is to say, all the sound sources must be confined to the other side; but it is not easily to achieve on industrial measurements. The technique builds the sound field separation formula in wave number domain according to the wave field extrapolation theorem, and the sound pressure caused by sources on one side of holographic plane can be obtained as expected by taking two-dimensional Fourier transform of the formula. The derivation of the principle verifies the technique theoretically, and the numerical simulations demonstrate its feasibility and effectiveness.