Cobalt antidot arrays with different thicknesses are fabricated by rf magnetron sputtering onto porous alumina substrates. Scanning electron microscopy and grazing incidence x-ray diffraction are employed to characterize the morphology and crystal structure of the antidot array, respectively. The temperature dependence of magnetic properties shows that in the temperature range 5D-300K, coercivity and squareness increase firstly, reach their maximum valus, then decrease. T he anomalous temperature dependences of coercivity and squareness are discussed by considering the pinning effect of the antidot and the magntocrystalline anisotropy.