To investigate the characteristic strength of single calcareous sand under the quasi static load， a high-precision single- particle loading apparatus was manufactured to carry out a series of single particle crushing tests on the calcareous sand with different size and shape obtained from South China Sea. Then the measured data were further statistically analyzed with the Weibull distribution function and the strength of single calcareous sand is normalized. The results show that failure mode of the single calcareous sand can be classified into three modes from the force-displacement curves， i.e.， hardening mode， softening mode and flat mode. The compressive strength of the single calcareous sand decreases with the increasing particle size and it is higher for block particles than that for flake particles at the same particle size. In addition， the strength distribution of the single calcareous sand shows a good agreement with the Weibull distribution， where the Weibull modulus m lies into the range of 1 ~ 3.