Abstract: In this paper a principle and method of estimating ultrasound attenuation spectrum from a backscattering echo are described.A series of experimental studies on fresh in vitro animal soft tissues have been completed by using the established in our laboratory automatic spectrum measuring system.The obtained results show that the measurement accuracy and precision are satisfactory.It is pointed out that this method of estimating attenuation spectrum,as one can be used for ultrasound tissue characterization,is of worth to study.