The precision filter mainly removes oil, liquid water mist, dust in compressed air. This series of products have three characteristics, they are high efficiency, convenient to use and low operating cost. This product is divided into C, T and A three grades according to different stages. The filtering precision of grade C is less than 3μ M except for 99.9 percent of moisture at free state, the filtering precision of grade T is less than 1μ M except for 99.99 percent of moisture at free state, and the filtering precision of grade A is less than 0.01μ M except for 99.999 percent of moisture at free state.