The invention discloses a method for detecting and purging residual oil on the plate surface of strip steel. According to the method, a rolling mill tail machine frame, the strip steel, a high-speed line scanning CCD camera, a purging spraying beam and a control unit, the high-speed line scanning CCD camera moves in the width direction of the strip steel and is arranged above the part, at an outlet of the rolling mill tail machine frame, of the strip steel, and the purging spraying beam is arranged at the outlet of the rolling mill tail machine frame and is arranged in front of the high-speedline scanning CCD camera. The method for detecting and purging the residual oil with the steel plate surface can be used for detecting and purging the residual oil on the plate surface of the strip steel has the advantages that the situation of the residual oil on the plate surface of the strip steel can be effectively quantified, the defects such as oil patches and white patches can be identifiedin a high-precision mode, and in addition, the defects can be rapidly eliminated by increasing the local purging pressure.