Abstract: Calcareous sand acoustic emission was tested under undrained condition to study the law of acoustic emission with different confining pressure, shear rate, initial void ratio and grading. The results showed that when the confining pressure was lower than 400 kPa, calcareous sand acoustic emission event rate increased with confining pressure. But when the confining pressure was increased to 800 kPa, calcareous sand acoustic emission event rate decreased. The test of calcareous sand was divided into particle breakage stage and particle slip stage in low shear rate. Two stages can't be distinguished clearly as the shear rate increases. Loose and dense calcareous sands have similar acoustic emission activities which were higher than medium dense calcareous sand. When grading of calcareous sand was well, acoustic emission peak appeared at the early stage of shear failure rate. When grading calcareous sand was poor, acoustic emission rate was relatively uniform, and acoustic emission peak appeared at the end of the test.