Abstract: The paper applies AR cepstrum to process the back scattered signals of normal and pathological human spleen in vitro,and the mean scatterer spacing(MSS)has been estimated.The results show that the MSS of two tissues is quite different and the AR cepstrum is effective to reflect the microstructure feature of tissue.Therefore,the AR cepstrum can be considered as an effective method for signal analysis of ultrasonic scattering and characterization of tissue scatteres.