Abstract: otoacoustic tomography (PAT) has the potential for the quantitative assessment of bone microstructure. However, due to the distributed solid-liquid two-phase porous structure of cancellous bone, the PA signals in the traditional PAT system are overlapped, which increases the difficulty and complexity of the quantitative analysis of bone microstructure. To solve this problem, the PAT system is improved to the eccentric excitation-differential detection mode to obtain the differential attenuation spectrum (DAS). The correlation between the porosity of cancellous bone and the characteristic parameters of PADAS is calculated and verified by using numerical simulation. The results show that there is a strong linear correlation between the characteristic parameters of photoacoustic attenuation spectrum and bone porosity, which indicates that the analysis method of the photoacoustic differential attenuation spectrum could effectively realize the quantitative evaluation and diagnosis of bone.