The oil contamination detector adopts advanced shading technology. The instrument consists of a light source, a particle sensor, a signal processing unit, a particle volume measurement system, a data output module and other components. The instrument can comprehensively monitor the size and number of single solid particles in the liquid. It intelligently classifies oil contamination particles and gives an evaluation grade based on preset standards. The unique design can effectively eliminate the impact of bubbles and moisture in the oil on the test results.