In this paper, a series of the gyromagnetic ferrite Li0.43Zn0.26Ti0.12MnxFe2.19−xO4 (x = 0–0.14) samples were prepared with the solid-phase reaction sintering method. The influences of Mn3+ doping on the microscopic morphology, ferromagnetic resonance linewidth, and microwave dielectric loss of LiZnTi ferrite were investigated. Doping in an appropriate amount of Mn3+ will reduce the saturation magnetization of the sample and the magnetocrystalline anisotropy of the ferrite. It also inhibited the generation of Fe2+ and reduced the porosity, to the benefit of keeping the ferromagnetic resonance linewidth (ΔH) of the material and microwave dielectric loss at a low level. The results suggested that when the doping amount of Mn3+ is 0.08, the ferromagnetic resonance linewidth of the material is 27.8 × 103 A m−1, the microwave dielectric loss tangent tanδ ε equals to 0.001, and the B-H hysteresis loop remanence ratio of the sample reaches 0.87, which is a beneficial application in lock-type microwave ferrite devices.