The utility model provides a machine oil filtering apparatus for filtering machine oil in an oil pumping unit reducer. The machine oil in the reducer passes through an oil pumping rubber tube, an agglutination/separation filter, a trash removal strainer filter, a gear oil pump, a fine filter, an electromagnetic valve and an oil outlet rubber tube and then enters the upper part of the reducer in a spraying manner. The machine oil filtering apparatus provided by the utility model can realize that the machine oil in the reducer can be purified and filtered, and the oil can be filled in the reducer in a purifying way. The machine oil in the bottom of a reduction gear box is pumped through operating a gear wheel pump, and the machine oil is filtered by a primary filter in a primary manner and then is discharged to enter the reducer. According to the machine oil filtering apparatus, the machine oil is effectively purified in an apparatus operation process, the fine impurities in an oil plant can be cleaned timely, the machine oil quality is improved, the safety economical operation and the complete machine service life of the apparatus are guaranteed, and the apparatus repair expense is effectively saved.