M-type strontium hexaferrites of Sr1-xLaxFe12-xMnxO19 (0.0 <= x <= 0.4) were synthesized by the chemical coprecipitation method. X-ray diffraction (XRD) studies indicate that the samples are single-phase with the space group of P6(3)/mmc. The results of field-emission scanning electronic microscopy (FE-SEM) show that the grains are regular hexagonal platelets with sizes from 0.7 to 1.4 mu m. It is observed that the value of H-c increases at lowsubstitution (x <= 0.1), reaches a maximum at x = 0.1 and then decreases at x >= 0.1, while the value of M-s decreases monotonously with increasing x. The variations of magnetic properties can be tentatively attributed to the effects of La-Mn substitutions. The results above indicate that our samples might be promising candidates for permanent magnets in the future. (C) 2018 Author(s).