NOVELTY - A biogas slurry pre-processing method comprises purifying the biogas slurry using filter material layers comprising a pebble first layer (7) having a grain size of 3-5 cm and thickness of 5-10 cm, a small rubble second layer (8) having a grain size of 1-1.5 cm and thickness of 20-25 cm in thickness, a coarse sand third layer (9) having a grain size of 2-4 mm and thickness of 20-25 cm, a fine sand layer (10) having a grain size of 0.1-2 mm and thickness of 10-20 cm, and a pebble fifth layer (11) having a grain size of 3-5 and thickness of 5-10 cm.    USE - Method of biogas slurry pre-processing (claimed) for foliar fertilizer or trickle irrigation fertilizer.    ADVANTAGE - The method prevents blockage of equipment caused by the fertilizer, solves automation of biogas slurry treatment and biogas slurry application, saves water and fertilizers, and reduces labor cost.    DETAILED DESCRIPTION - A biogas slurry pre-processing method comprises:    (A) pumping biogas slurry in the biogas slurry collecting pool to a biogas slurry pre-processing pool using an automatic control device (2);    (B) purifying the biogas slurry using filter material layers comprising a pebble first layer (7) having a grain size of 3-5 cm and thickness of 5-10 cm, a small rubble second layer (8) having a grain size of 1-1.5 cm and thickness of 20-25 cm in thickness, a coarse sand third layer (9) having a grain size of 2-4 mm and thickness of 20-25 cm, a fine sand layer (10) having a grain size of 0.1-2 mm and thickness of 10-20 cm, and a pebble fifth layer (11) having a grain size of 3-5 and thickness of 5-10 cm; and    (C) discharging purified slurry from the biogas liquid pre-processing pool though water discharge tube on one side of the bottom part and transporting to biogas slurry blending pool.    An INDEPENDENT CLAIM is included for a device of biogas slurry pre-processing method comprising:    (1) a biogas slurry collecting pool;    (2) an automatic control device comprising a block-free sump pump and a power distribution system;    (3) a biogas pre-processing pool comprising filter material layers; and    (4) a biogas blending pool (4).    DESCRIPTION OF DRAWING(S) - The drawing is a schematic sectional view of biogas pre-processing pool.    Pebble first layer (7)    Small rubble second layer (8)    Coarse sand third layer (9)    Fine sand layer (10)    Pebble fifth layer (11)