The invention discloses a porous film which comprises a filtering layer and a porous support, wherein the filtering layer is composed of dendritic metal substance powder and/or metal substance oxide powder. A preparation method for the porous film comprises the following steps: 1) acquiring the raw material powder and the porous support, wherein the raw material powder is the dendritic metal substance powder and/or the metal substance oxide powder; 2) preparing slurry; 3) loading the slurry on the surface of the porous support, drying and preparing into a film blank; 4) sintering the film blank and cooling, thereby acquiring the porous film. Firstly, the dendritic metal substance powder is stacked and formed into the pores of the porous film, the complex hole-forming process is avoided and the porosity is high and is easy to control; the filtering layer composed of the dendritic metal substance powder and/or the metal substance oxide powder is stable in physico-chemical property, long in service life and free from mutual reaction; the complex phase-forming process is avoided; the component of the porous film is easy to control.