In the context of ocean engineering development, the utilization of calcareous sand as a natural foundation has become indispensable. Therefore, in this paper, one-dimensional compression tests were conducted on three different grain size groups of calcareous sands to analyse the progressive evolution and impact of particle breakage. The findings of the tests reveal intriguing patterns. An inflection point is identified in the e-log(p) curve, indicating the onset of grain fragmentation, leading to a steeper curve slope. Notably, larger-grain calcareous sands exhibit heightened susceptibility to breakage compared to their smaller-grain counterparts. This vulnerability can be attributed to their higher internal porosity and inherent defects. Among calcareous sands of identical grain groups, increasing vertical stress induces a gradual shift in the Particle Size Distribution (PSD) curve. This shift may even generate particles smaller than 0.075 mm, causing an increase in the Br*(Einav) value. Furthermore, as Br* value rises, the e-log(p) curve gradually descends.