The invention belongs to the technical field of agriculture, and particularly relates to a method for soil improvement and remediation by using a 'quaternary' method, a compound microbial agent used in the method, and application of the compound microbial agent in soil improvement and remediation. The 'quaternary' soil improvement and remediation method starts from organic matter improvement, mineral substance improvement, biodegradation and disease resistance and growth promotion, and comprehensive improvement and remediation are carried out on soil in four aspects of soil physical structure, chemical nutrients, biological activity and soil-borne diseases through deep soil improvement and shallow soil remediation. The activity of soil carbon-nitrogen cycle related enzymes can be remarkably improved, the soil microbial population structure is optimized, the soil microbial function is improved, plant residues in soil are driven to be fermented through the interaction of disease-resistant probiotic microorganisms, beneficial microorganisms become main force of soil activity, the soil structure is improved, land is fully utilized, and the method is of great significance in sustainable development of agriculture, improvement of the income level of farmers, improvement of life of people, protection of ecological environment and the like.