Abstract: A high speed digital data acquisition and wide band measurement system was used to acquire and record the ultrasonic pulse waveforms backscattered from normal and several pathological pig's fresh liver tissues (including ballooning degeneration, fatty degeneration, cirrhosis) in vitro. Some frequency domain analyses in the frequency domain ranging from 3MHz to 7MHz were performed in which the integrated backscatter coefficient (IBSC), the frequency dependence of backscatter coefficient (FDBSC), and the mean spacing (MS) among adjacent scatterers of the tissues were determined. The results obtained show that the differences among the normal and various pathological tissues cause distinct changes of the measured parameters. All the results studied indicate that the ultrasonic spectrum technique, which can be used in tissue characterization for pathological liver in clinics, has an encouraging prospect.