The invention provides a filter layer and a mask, and relates to the field of new materials. The filter layer is compounded of nanofibers threaded into the inside of carriers of three-dimensional multi-hole structures. In the filter layer, the nanofibers threaded into the three-dimensional multi-hole structures are matched with the carriers, so that the filer layer not only maintains a certain porosity but also has the advantages of mall resistance and good filtering effect. The mask made of the filter layer combines the advantages of high respiration comfort and high filtering performance.