Abstract: From both academic and practical points of view,the investigation of different microstructures by nondestructive ultrasonic methods had been a topic of interest recently.In the present work,an experimental immersion beam focus technique had been developed to measure relative attenuation of ultrasonic waves through non-quenched and tempered 30Mn2SiV steel for sucker rod with different mixed microstructures.A relationship between relative attenuation and mixed microstructure of 30Mn2SiV steel for sucker rod was investigated.And the results indicate that the order of ultrasonic relative attenuation in specimens is as follows:upper bainite>lamellar pearlite + ferrite>globular pearlite.