Abstract: In order to study the filtration mechanism of the moisture separator for water droplet of 5～10μm,this paper set up a physical model.For the mixed meshes,they can be classified into three types: standard meshes,bur meshes and middle meshes.For all fibers of the wire meshes and vertical fibers of standard mixed meshes,a Kuwabara flow field is used to track the particle to get the inertial impaction efficiency and then calculate the total filtration efficiency of the meshes.For other fibers,besides the Kuwabara flow field,an around-flat flow field is added to calculate the efficiency.Lastly,the total efficiency of the moisture separator according to the equation of the filtration efficiency for the filters in series is compared with the experimental data.The result shows that,under the standard condition,the calculation value is consistent with the experimental efficiency data.