The invention discloses compound fertilizer for farmland soil improvement and a preparation process thereof. The compound fertilizer is prepared from the following components in parts by weight: 3-6 parts of a microbial compound inoculant, 6-10 parts of earthworm egg cocoons, 15-20 parts of cow dung, 5-7 parts of compost zymophyte, 20-30 parts of straw, 15-20 parts of mushroom residues, 20-25 parts of rotten figs, 15-20 parts of fresh durian shells, 20-25 parts of a sugar residue mixture, 18-25 parts of bentonite, 15-20 parts of diatomite, 8-12 parts of emulsified asphalt, 10-15 parts of distillers' grains, 5-7 parts of sulfur powder, 8-10 parts of ferrous sulfate and the balance of rice washing water. Earthworm egg cocoons are introduced into soil and can be rapidly hatched into earthworms after the fertilizer is put into use, formation of a soil aggregate structure is promoted, soil breathability is improved, and the soil fertility level is increased. The organic fertilizer improvesthe physical and chemical properties of the soil and enhances the fertilizer retention performance and buffer performance of the soil, the number and activity of soil microorganisms are increased, thesoil temperature is increased, the soil ion exchange rate is increased, and rice washing water is used as a solvent to promote crop growth.