Abstract: Plasma sprayed method was used to prepare Cr2O3 coatings on stainless steel and the depth of the coatings were 50 μm. The porosity and distribution of micro-cracks of the coatings were changed by high-intensity pulsed ion beam(HIPIB). The reflection wave signal and the reflection coefficient spectrum of the coatings before and after irradiation were obtained using ultrasonic immersed focusing method, the relationships between ultrasonic attenuation coefficient and frequency of the coatings before and after irradiation were compared. The results indicate that the relationships of the coatings before and after irradiation were α=0.28f+9.50×10-4f2+7.04×10-6 and α=0.11f+2.10×10-4f2+8.73×10-6f4, the data fitting results accord with the examination results, and the ultrasonic characterization results accord with SEM photos basically.