An ultrasonic etching method is effective to pretreatment of PVC plastic for plating without chemical pollution. After being etched for 60 min by 28-kHz ultrasound, the improvement of adhesion strength of Cu-PVC can increase 13%, compared with that of chromic-sulphuric acid etching. The mechanism of adhesion improvement was studied by examination of weight loss, surface roughness, scanning electron microscopy, image analysis, and X-ray photoelectron spectroscopy.