The mineral formation-transition mechanism, microstructure evolution, crystal structure, pulverization property, and chemical reactivity of the CaO-Al2O3-SiO2 clinker with MgO and Na2SO4 dopants during the sintering process at 1300 °C for 2.0 h were systematically studied using CaO, Al2O3, SiO2, MgO, and Na2SO4 as raw materials when the molar ratio of CaO to Al2O3 is 1.4, the mass ratio of Al2O3 to SiO2 is 3.0, and the mass percentage of MgO and Na2SO4 is 2%. The MgO dopant could result in 12CaO·7Al2O3 and γ-2CaO·SiO2, transform into 20CaO·13Al2O3·3MgO·3SiO2, restrain the crystal transformation of 2CaO·SiO2 from β to γ, and then deteriorate the pulverization and alumina leaching property corresponding to parts of Al, Si, and Mg atoms occupying the same lattice positions of the crystal structure. MgO and Na2SO4 codoped could promote transformation of 20CaO·13Al2O3·3MgO·3SiO2 into 3CaO·3Al2O3·CaSO4 as well as some 2CaO·Al2O3·SiO2, while 3CaO·3Al2O3·CaSO4 has good alumina leaching property in the Na2CO3-NaOH solution. The ultrasonic assistant mainly could promote the diffusion of reactive samples, enhance the separation of agglomeration, and then accelerate the chemical reaction of the sintered clinker with Na2CO3-NaOH.