Abstract: For the study of establishing a theoretical model which aims at predicting ultrasonic attenuation of elastic, spherical mixing particles in the liquid-solid two-phase system, the Monte Carlo Method (MCM) is introduced, serving as a probability and statistics technique. On the basis of ultrasonic scattering and aborption, the continuous ultrasonic waves are represented as discrete and independent phonons. By tracing the movement and scattering events as well as calculating the number of phonons which finally reach the receiving transducer, the ultrasonic attenuatioil coefficient is finally obtained. Numerical investigations have been carried out to predict and compare the ultrasonic attenuation for a solid-liquid two-phase system with a single type particle. Apply such method into mixing particle system after ensuring its feasibility. Then, the mixing iron and glass bead particles with various ratios are set as examples for the purpose of predicting ultrasonic attenuation for the monodisperse and polydisperse mixing particle systems. Tile results of MCM, the ECAH model, the Lloyd&Berry model and the Waterman model match well when the particle volume concentration is lower than 10%, corresponding to iron and glass bead respectively. In the case of two-phase system with mixing particles, it is shown that as the particle volume concentration increases to 10%, the variation of the ultrasonic attenuation coefficient with mixing ratio yields a nonlinear tendency. The nature of particles can also influence ultrasonic attenuation significantly.