The coefficient of earth pressure at rest K₀ is an important parameter for geotechnical engineering. In order to study the influencing factors and mechanisms of peat soil K₀, a K₀ consolidation instrument was used to conduct a lateral compression test on Kunming Dianchi peat soil. The effects of vertical stress, organic matter content and initial void ratio on K₀ were systematically analyzed, and from the structural perspective, the formation mechanism of its K₀ change law was explored. The test results show that the coefficient of earth pressure at rest of reshaped peat soil is not a constant, but is related to the vertical stress and content of organic matter; K₀ decreases with the increase of vertical stress during loading and finally tends to be stable. The decreasing trend of K₀ under stress is more significant; under the same vertical stress, the greater the organic matter content of the soil sample, the smaller K₀, and the greater the decrease in K₀ during the entire loading process; the dynamic changes in the structural properties of peat soil during the loading process are the fundamental cause of changes in K₀. Vertical stress and organic matter affect K₀ by affecting its structural properties, and there is a certain coupling relationship between the two; the K₀ value after stabilization of reshaped peat soil is between 0.42 and 0.6, which is lower than that of inorganic clay, and has a linear negative correlation with the organic matter content. Based on the experimental results, a corresponding fitting relationship is proposed; the relationship between the initial void ratio and the K₀ value is relatively discrete.