Abstract: Quantitative detection of scatters in millimeter or micron scale is an important topic in the field of industrial manufacturing, medical diagnosis and treatment. In this study, millimeter scale elastic spheres were regarded as the detection targets, the shape function f_∞(π) and the target strength T_S are numerically calculated, and the influence of material and radius are also analyzed. In order to solve the multi-value problem between T_S and the radius a, a solution is proposed by using the difference frequency superposition of scattering signal intensity to attenuate or even eliminate acoustic interference and realize the quantification of scattering radius. The results show that the superposition method can effectively attenuate the acoustic interference in a certain bandwidth, and the experimental results also confirm that the radius of millimeter spherical scatters can be quantified by measuring the strength within a certain precision.