The invention relates to the technical field of oil extraction treatment and especially relates to a system for ultrasonically treating an oil field. The system comprises an oil layer positioning device and an ultrasonic treatment device, wherein the oil layer positioning device comprises an oil layer positioning emitter and an oil layer positioning recognizer; the ultrasonic treatment device comprises an oil layer positioning receiver, a laser component, an ultrasonic wave generator, an energy converter, a light reflecting tube and a metal tube, wherein the light reflecting tube is located at the inner side of the metal tube; the laser component is located at one side of the metal tube; the energy converter is located at the outer side of the metal tube; the ultrasonic wave generator is connected with the energy converter; the laser component can emit laser light; the laser light is repeatedly reflected by the light reflecting tube so as to form a light column; under the effect of the ultrasonic wave generated by the ultrasonic wave generator, and the laser non-reflection, reflection and scattering are enhanced, so that the chromatic dispersion can be enhanced by the laser light, the crude oil can be effectively separated, no pollution is caused and the resource is effectively saved.