We applied spin-waves resonance technique in order to determine the temperature dependence of the surface magnetic anisotropy energy constant for thin films of CdCr 2 Se 4 diluted by In. The n M of the close-to-surface layer contributes to the surface magnetic anisotropy energy originated from the surface demagnetizing field with an anisotropy energy constant K s d = 4πM 2 ( n M/M)d 2 , where d is the thickness of the close-to-surface layer. We have found within the temperature range 4.2-80 K, that K s d is linearly decreasing when the temperature is increasing.