The puroose of the study was carried out to investigate the change of bacterial growth in vitro according to intensities and exposure time. to basic data far ultrasound and clinical research. The Staphylococcus aureus which are commonly isolated from open wound were incubated in an incubator for 24 hours following expoure 1MHz continuous ultrasound(CUS). Then quantitative bacterial counts were obtained. The results were as following. 1. The groups CUS was appied changed in bacterial growth according to intensities and time respectively. 2. The groups CUS was appied showed the inhibitory effect of bacterial growth. 3. The number of S. aureus significantly reduced to fellowing expoure $3.0w/cm^2$ CUS during 20min.