This work aimed to synthesize and characterize some calcium aluminate phases via sol–gel method. These phases were produced by mixing calcium and alum inum nitrates salts [Ca(NO3)2·4(H2O) & Al(NO3)3·9(H2O)] which have been used as starting raw materials to prepare nano-oxides composite of CaO as well as Al2O3 in different molar ratio for synthesizing CA, C2A and C3A pure phases via Sol–Gel method. The produced powder has been investigated by X-ray Diffraction (XRD), Dynamic Light Scattering (DLS), Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM) and Thermal Gravimetric as well as Differential Thermal Analyses (TGA & DTA) techniques. The influence of phase composition, calcination temperature as well as the calcination period on the phases’ characters was also studied. In addition, the microstructure and the physico-mechanical properties of hydrated phases have been studied. This study concluded that, using nano size starting materials led to the formation of CA and C3A phases at 1000/1h and 1200 ◦C/2h, respectively which were lower than the traditional methods, while the C2A phase could not be formed under the normal condition. The crystalline calcium aluminate phases have been formed at earlier calcination temperature with increasing CaO molar ratio.