The phase?transformation process form 25°C to 1450°C and magnetic properties of Sr0.3La0.3Ca0.4Fe10.625Co0.225Zn0.1O19 were investigated by means of high-temperature X-ray diffraction, thermal analysis, vibrating sample magnetometer and scanning electron microscopy. The formation of M-type hexagonal ferrites in air passes through two endothermal reactions. SrCO3 and partial Fe2O3 first generated the intermediate phase Sr3Fe2O7-d in around 700°C. And then Sr3Fe2O7-d and the remaining unreacted Fe2O3 generated SrFe12O19. Meanwhile, La3+, Ca2+, Co2+ and Zn2+ ions gradually dissolve in the intermediate phase or the late product M phase with the temperature increases. The perovskite was obtained when annealed at about 700°C, which may transform perovskite into Sr3Fe2O7-d during the cooling process. The average valence of Fe in Sr3Fe2O7-d was a function of temperature. A very high single degree of M phase and a small number of second phase were obtained at about 1200°C, and the cationic were evenly distributed in the crystal. The rectangularity of the demagnetizing curves of the LaCaCoZn-type substituted ferrite powder decreases compared to that of unsubstituted ferrite powder. The ferrite will be decomposed at about 1380°C.