Mn ferrite powder (MnFe2O4) were prepared by the wet chemical co-precipitation method and after-ward annealed in air. The effects of heat treatment temperature on crystalline phases formation, microstructure and magnetic properties of MnFe2O4were investigated by X-ray diffraction, Fourier-transform infrared spectroscopy, Scanning Electron Microscopy and SQUID. All annealed sample showed pure ferrite phase, larger saturation mag-netization was observed at 900°C (Ms=75.1emu/g) and lower coercivity (Hc= 33.04 Oe) compared with the co-precipitated ferrite powder at 700°C (Ms=44.32 emu/g, Hc = 62.6 Oe). The 600°C air-annealedsample had the largest blocking temperature (Tb = 10.88 K). Field-dependentmagnetization measurements show low coercivities with no remanence giving additional proof for the superparamagnetic behavior. It is also observed that with increasing an-nealing temperature the Tcvalue also increases.