Nano-structure CoxFe3-xO4 porous microspheres are synthesized in ethylene glycol (EG) solution, using FeCl3·6H2O, CoCl2·6H2O and NH4Ac as the starting materials through solvothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are used to characterize the structures of synthesized products. The results show that monodisperse CoxFe3-xO4porous microspheres with polycrystal structures are assembled by nanoparticles, and the average diameters is about 300 nm. The magnetic properties are evaluated with a vibrating sample magnetometer (VSM). The results indicate that the saturation magnetization ( Ms) and the Curie temperature (Tc) first increase and then decrease, and the coercivity (Hc) increase with the increase of Co2+ content. According to the hysteresis loops at different temperatures, CoxFe3-xO4 porous microspheres possess remarkable exchange bias effects at low temperatures.