Abstract: Crude oil must be desalted and dewatered before refined in oil refinery.Emulsion breaking by sound wave is an effective demulsifying method which reinforcing dehydration and desalination of crude oil emulsion.The effects of sound wave intensity and irradiation time on Lu-ning crude oil emulsion dem-ulsifying are investigated in standing sound wave field.The preferable experimental conditions involve the following:crude oil temperature 80℃,rotational speed 400r·min^-1 and time 5min,demulsifying agent dosa-ge 20μg·g^-1,water injection rate 5%,sedimentation temperature 75℃ and time 90min,ultrasound intensity 0.38W·cm^-2.Under these conditions,water content is decreased to 0.37% by volume,salt content 3.85mg·L^-1.Dehydration ratio is 92.6% and desalination ratio 87.9%.Salt balance of crude oil finds that less water injection rate leads to higher salt content in crude oil emulsions if other experimental conditions are the same.The reason is that less water results in less contact chances of water and crude oil.