The oil contamination tester is designed using the principle of light blocking method (light blocking method) to detect the size and quantity of particles in the liquid. It can be widely used in aviation, aerospace, power, petroleum, chemical, transportation, ports, metallurgy, machinery, automobile manufacturing and other fields for solid particle pollution detection of hydraulic oil, lubricating oil, transformer oil (insulation oil), turbine oil (turbine oil), gear oil, engine oil, aviation kerosene, water-based hydraulic oil and other oils, as well as for insoluble particle detection of organic liquids and polymer solutions.