Co-ferrite ($CoO-Fe_{2}O_{3}$) thin films have been prepared by two ways of low temperature solid reaction including oxidation process, being based on $Co-layer/{alpha}-Fe_{2}O_{3}$ films and $Co-layer/Fe_{3}O_{4}$ films. Magnetic properties of both Co-ferrite films have been measured and compared. The samples from $Co-layer/Fe_{3}O_{4}$ films have a large coercive force in the direction perpendicular and have a great poler kerr rotation angle at wavelength 700 nm than ones from $Co-layer/{alpha}-Fe_{2}O_{3}$ films. The typical magnetic properties are as follows; saturation magnetization $4{pi}Ms$, 2.9 kG; remnant magnetization $4{pi}Mr$, 2.0 kG; coercive force Hc, 4.0 kOe; kerr rotation angle ${PHI}k$, 0.39 deg($lambda;=;700;nm$); and initial magnetization energy E, $3.3;{ imes};10^6;erg/ extrm{m}^3$, respectively.