Abstract: With regard to the poor axial ultrasonic transmission of the LZ50 and C35e axles, the axles of the corresponding specification varieties with the same process and the same grain sizes were anatomically analyzed. The results show that the regional pearlite aggregation or regional distribution of pearlite and ferrite group (locally accompanied by needle-like ferrite) exist in the metallographic structure of poor axial ultrasonic transmission axles. On the other hand, a uniformly distributed pearlite and ferrite fine grain structure exists in the metallographic structure of axles with qualified ultrasonic transmission. Practice shows that the pearlite aggregation or the regional distribution of pearlite, ferrite group will make the axial ultrasonic scattering attenuation increase, and the influence of such microstructure on axial ultrasonic scattering attenuation is greater than locally single great grain. In practice, billet smelting, rolling and axle forging and heat treatment should be effectively controlled to eliminate or weaken the existence of this kind of structure.