A low-cost and high-efficiency solid reaction method has been reported as an effective technology to synthesize manganese ferrite MnFe₂O₄ with a spinel crystal structure. This work clarified the underlying reason for the influence mechanism of SiO₂ and Al₂O₃ on the synthesis of MnFe₂O₄. Synthetic MnFe₂O₄ polyhedral microparticles with a saturated magnetization of 71.19 emu/g, a ratio of saturation magnetization to residual magnetization (Ms/Mr) of 0.062 and a coercivity (Hc) of 6.50 Oe were successfully obtained at an oxidization roasting temperature of 1100 °C for 60 min. The experimental results indicate that the tetrahedral Mn²⁺ ions and octahedral Mn³⁺ ions in the crystal structure of manganese ferrite MnFe₂O₄ were replaced by tetrahedral Si²⁺ ions and octahedral Al³⁺ ions from (Mn²⁺)_x(Fe²⁺)_y(Si²⁺)_1−x−y[Fe³⁺]₂O₄ and (Mn²⁺)[Fe³⁺]_2−x[Al³⁺]_xO₄, respectively. In addition, hercynite Fe_xMn_1−xAl₂O₄ with a spinel crystal structure and olivine Mn_xFe_2−xSiO₄ with an orthorhombic crystal structure were partially formed in the synthesis of manganese ferrite MnFe₂O₄, in which some Fe²⁺ ions were easily replaced by Mn²⁺ ions to form stable hercynite MnAl₂O₄ and olivine Mn₂SiO₄ in these crystal structures. The current research work provides comprehensive insights for synthesizing manganese ferrite MnFe₂O₄ and continuously advances its technical progress.