The invention discloses a subsoiling flat cutter weeding and soil preparation machine, which comprises a suspension frame, a machine frame, an earth wheel, a subsoiling shovel, a transmission mechanism and a weeding and soil preparation machine, wherein the transmission mechanism consists of a transmission shaft, a gearbox, an eccentric shaft, a connecting rod, a swinging arm, a weeding cutter leg and a machine frame, and the weeding and soil preparation mechanism comprises a weeding cutter leg, a weeding flat cutter and a separation grid sieve. The subsoiling and the flat cutter weeding and soil preparation are optimized and combined, the combined operation of subsoiling, weeding and soil preparation is realized through one-step operation, the damage to the soil structure is small through the flat cutter weeding, the soil layer disturbing is small, the operation moisture loss is little, the moisture preservation effect is good, the weeding is overall and thorough, and the weeding effect is good. The grass roots and residue stubbles and roots cut by the weeding flat cutter are separated from the soil and cover the earth surface through the separation grid sieve, the surface layer soil layer structure cannot be damaged, the soil moisture loss is little, the earth surface is smooth after the operation, the earth surface residue stubble coverage rate is high, the effects of weeding and earth surface straw residue stubble coverage maintaining are reached, and the effects of water storage and moisture preservation, sand storm prevention, moisture evaporation reduction and the like are realized.