The invention discloses controllable mixed nano filament filter paper as well as a preparation method and application thereof. The method comprises the following steps: (1) separately preparing plantcellulose paper pulp A, B, and C with a mass concentration of 0.1 to 15 percent, and grinding by adopting an ultra-micro-particle crusher to obtain plant micro-nano filaments A, B and C, wherein a gapof the ultra-micro-particle crusher is -200 micrometers to 150 micrometers, the grinding period is 1 to 70, and the rotation speed is 100 to 2500 r/min, and when the plant cellulose paper pulp A, B and C are ground, the gap, the grinding period and the rotation speed of the ultra-micro-particle crusher are not completely same; and (2) uniformly mixing the plant micro-nano filaments A, B and C, and then performing the papermaking, thus obtaining the controllable mixed nano filament filter paper. The porosity and aperture of the filter paper can be adjusted by changing the ratio of the three nano filaments, so that the requirements of different products can be met.