High performance of filter media is the key to achieve good performance which can filter in 5-20 micron range. The oil air separation can be made up of different layers. The first layer is usually a fine separation layer, which is made of borosilicate glass fiber with certain thickness and pore. This kind of micro high-precision glass fiber, which can hardly be bonded, can ensure the stability of different lubricants, even at higher operating temperature. The conductivity of oil drop is realized by polyester fiber. When the pre-separation condition of the oil separator is not good, the pre-separation layer installed on the surface of the oil air separator filter can prevent the other two layers from overloading and extend the service life of filter.