Although the research of high entropy alloys (HEAs) has become a hot spot due to their excellent mechanical properties, the grinding properties of HEAs have not received as much attention as they should. In this study, the grinding properties of AlCoCrFeNi2.1 dual-phase HEA with diamond grinding wheel were studied experimentally. The single-factor grinding experiment was carried out to carefully record the grinding force and grinding surface roughness with different grinding parameters, including grinding wheel granularity, grinding wheel linear speed, feed speed, and grinding depth. Moreover, the morphology of the grinding surface, subsurface, and grinding chips was observed and the effects of grinding parameters on the defects of the grinding surface, the microstructure of the subsurface, and morphology of the grinding chips were analysed. Small abrasive grain size, high grinding wheel linear speed, low feed speed, and small grinding depth are more conducive to obtaining low grinding force and surface roughness, causing few grinding surface defects, reducing the thickness of the deformed layer on the subsurface, and forming the banded grinding chips caused by plastic deformation. This work is helpful to provide theoretical guidance and data support for the grinding of AlCoCrFeNi2.1 dual-phase HEA.