Abstract: This paper aims to reveal the compressive deformation,particle breakage characteristics,and acoustic emission laws of calcareous sand. The one-dimensional compression-resilience tests and synchronous acoustic emission tests were carried out on calcareous sand with different particle size fractions under three different relative densities. By sieving analysis,the relative breakage(B_r) was obtained based on the particle size distribution after the test. The experimental results showed that the compressive deformation of calcareous sand is caused by the particle rearrangement and particle breakage. The particle breakage is the major factor behind this phenomenon. The rebound curve is approximately a straight line,indicating that the compressive deformation is an irreversible plastic deformation. Under the same stress,the larger the particle size,the greater the B_r. The different shapes of the particles result in different interparticle filling and interlocking effects,which affects the sliding and rearrangement of the particles,and then influences the compressive deformation of the particles. The acoustic emission counts rate of the two kinds of sand increases with the increase of the particle size,and both appear mainly in the compression phase between 800 kPa and 3200 kPa. The compressive deformation and breakage characteristics of calcareous sand are consistent with their acoustic emission laws. The relation curves between counts rate and time are in good agreement with the stress-time curves. The mechanical characteristics of the calcareous sand can be reflected based on the counts rate-time curves. For calcareous sand,a "critical void ratio" exists with the fewest acoustic emission events. In this study,its value of calcareous sand with a particle size of 1~2 mm is 1.33~1.41. When the initial void ratio of the sample deviates from this critical value,the acoustic emission activities would increase in varying degrees.