Abstract: Abstract: Soil provides the foundation of farmland ecosystems and is an important component of arable land. As well as providing a platform for plant growth, soil helps retain water, nutrients, and organic matter. Soil is also home to a variety of microorganisms and living organisms that play a key role in maintaining soil fertility. Healthy and active farmland soil play an important role in resisting soil erosion by rainfall runoff, wind, and snowmelt runoff. However, with the development of agricultural machinery to large, high-speed, low-consumption, joint operation direction, and the increase of the scale of agricultural mechanization in recent years, farmland soil has suffered from more serious mechanical compaction, which has become a global issue. In the process of agricultural operations, farmland soil is subjected to mechanical compaction, which has an impact on the soil’s physical properties, chemical properties, and soil biology. Mechanical compaction often makes farmland soil unsuitable for crop growth and reduces resist the ability to external erosion. Most studies found that mechanical compaction could increase soil bulk density, reduce soil porosity, weaken the stability of soil aggregates, reduce soil infiltration capacity, release soil nutrients, inhibit the ability of soil gas exchange, and break soil biological balance. It is worth paying attention to that the ability of farmland soil to resist erosion is also affected by the mechanical compaction of farmland operation. The influence of compaction on soil erosion resistance is mainly realized indirectly through the physical properties of compacted soil. This paper outlined the cause of mechanical compaction of farmland soil through describing the development of agricultural machinery and mechanical stresses on the soil, elaborated the effect of mechanical compaction on soil properties and their mechanism, and discussed the indirect effects of mechanical compaction on soil erosion. There are many researches on the effects of compaction on soil physical and chemical properties, but few studies on the effects of compaction on soil biology and the interaction between soil physical and chemical properties and soil biology. It is concluded that current researches mainly focus on the effects of mechanical compaction on soil properties and soil properties on soil erosion, but there are few studies on the mechanism of mechanical compaction on soil erosion. Finally, in view of the deficiencies of the current mechanical compaction researches, the future development direction of related researches in China is proposed. The most important is that current qualitative researches on mechanical compaction have been perfected and comprehensive. In the future, researches should pay attention to quantitative researches on the transformation process of soil to a special state by agricultural mechanical compaction under the unified standard. It should be considered that when designing experimental conditions are similar to the actual compaction conditions of agricultural machinery. When studying the effect of compaction on soil erosion, we should pay attention to the effect of compound erosion. The purpose of the above work is to better apply the existing researches theory of mechanical compaction to practice, seek advantages and avoid disadvantages, and also hope to provide a reference for the prevention and control of soil erosion in domestic farmland operations.