Filter paper can be divided into qualitative and quantitative two. In the application of analytical chemistry, when the inorganic compounds are separated by filtration, the residue collected on the filter paper can be used as the loss rate in the calculation process. The qualitative filter paper has more cotton fibers after filtration, so it is only suitable for qualitative analysis; Quantitative filter paper, especially the gray-level filter paper passes special procedures, can effectively resist chemical reactions, so the resulting impurities are less, can be used as quantitative analysis. In addition to the general laboratory application of the filter paper, the application of daily life and engineering filters are also many. Coffee filter Paper is one of the widely used filter paper, tea bags of the outer filter papers provide a high degree of flexibility and moisture intensity characteristics. Other air filters used in the test of suspended particles in the air, and fiber filter paper in different industrial applications.