Magnetic properties of La doped M-type barium ferrites are studied. The samples are prepared by the standard solid state reaction method. The influences of La3+ on structures and magnetic properties of barium ferrites (Ba1-xLaxFe12O19) are investigated. Single-phase M-type barium ferrites with chemical composition of Ba1-xLaxFe12O19 (x=0.0—0.6) are formed by sintering at 1100—1175 ℃ in air. Scanning electron microscopy (SEM) reveals that the La doping has no effect on the structure of barium ferrite. Vibrating sample magnetometer (VSM) shows that with the valaue of x increasing, the saturation magnetization (Ms) increases, reaching a maximum at x=0.2 and then decreases and the coercivity of the sample increases continuously. The value of Ms reaches a maximum value of 62.8 emu/g at x=0.2 and 1175 ℃, and the Hc reaches a maximum value of 3911.5 Oe at x=0.6 and 1125℃.