Abstract: Calcined diatomite/α-Fe₂O₃ composite particle materials (CD/α-F) were prepared with calcined diatomite and α-Fe₂O₃ as raw materials by a mechanochemical method in the system of wet grinding. Scanning electron microscopy, energy dispersive spectrometry, hiding power and oil absorption measurements were used to characterize the morphologies and pigment properties of CD/α-F. The reaction mechanism of the composite particles was analyzed by X-ray diffraction and Fourier transform infrared spectroscopy. It is shown that mechanochemical effect enhances the particle surfaces of calcined diatomite and α-Fe₂O₃ to form hydroxide radicals further, thus promotes dehydration-condensation reactions between hydroxide radicals from the two raw materials and then Si…O…Fe bonds form with weak linking forces. Moreover, the core-shell CD/α-F composite powder has similar pigment properties to pure α-Fe₂O₃ in experimental conditions desired.