Single phase Sr-La-Co M-type ferrite fine particles were prepared by the chemical coprecipitation and subsequent heat treatment. The chemical reagents used for an experiment are FeCl₃⋅6H₂O, Sr(NO₃)₂, La(NO₃)₃⋅6H₂O, Co(NO₃)₂⋅6H₂O and CoCl₂·6H₂O. The chemical coprecipitation composition were chosen according to the formula {(SrO)·n/2(Fe₂O₃)}100-x-y(La₂O₃)x(CoO)y, where n was fixed at 7.0 and x at 1.5 and y was varied between 1.0 and 10.0. A water solution containing Sr²⁺, Fe³⁺, La³⁺ and Co²⁺ was poured into solution of NaOH (pH=13.0). Aqueous suspensions containing the coprecipitated products were boiled for 2h, and they were carefully washed, filtrated and dried at 80°C for 12h. The obtained fine particles were heated 950 to 1100°C for 2h in air to get single phase Sr-La-Co M-type ferrite fine particles. The conditions determined as optimum for preparing the fine particles with the best values of σ_s=90.2×10^-6 Wb·m/kg (71.8emu/g), σ_r=45.1×10_-6 Wb·m/kg (35.9emu/g), H_cj=525.2kA/m (6.60kOe) and T_c=453.9°C are as follows: composition; Sr_2+0.812La³⁺_0.045Co²⁺_0.045Fe³⁺_9.236O^2-₁₉; heat treatment; 1000°C×2h in air, the average particle size; 0.3-0.4μm.