Abstract: At present, there are few apparatuses and methods applicable for measuring K₀ of coarse-grained soil, and the relevant research about the effect factors of K₀ for coarse-grained soil is almost blank. To investigate the effect factors of K₀ for coarse-grained soil, several K₀ tests for a sandy gravel were performed by using a newly-developed large-size K₀ apparatus. By changing the initial conditions such as initial relative density D_r0 and maximum grain size d_M, the K₀ behavior of coarse-grained soil under different experimental conditions is investigated. The test data show that:a linear negative correlation exists between K₀ and D_r0 for coarse-grained soil; a negative correlation exists between K₀ and d_M for coarse-grained soil, and the correlation can be expressed by a power function; K₀ trends to decrease with the increase of effective vertical stress σ'_v, and the effect of σ'_v on K₀ is more pronounced under low σ'_v.