Abstract CaO–Al 2 O 3 –MgO–SiO 2 ( CAMS )‐based glass‐ceramics were prepared using body crystallization method. Adding Cr 2 O 3 into the ceramics not only effectively lowered the crystallization temperature, but also led to significant grain refinement of diopside that crystallized in the CAMS glass‐ceramic after crystallization treatment at 900°C for 2 hours. Experimental work verified that the epitaxial growth of the diopside on the spinel particles, which formed during nucleation treatment when fabricating the glass‐ceramics, facilitated the heterogeneous nucleation of diopside on the spinel and refined the diopside. In addition, two energetically favored crystallographic orientation relationships between the epitaxial growth diopside and spinel were experimentally observed. They are //[001] diopside ,// //(200) diopside and //[101] diopside , (311) spinel // . These two novel results can be potentially used to develop new glass‐ceramic materials with improved performance.