Taking into account the effect of the generalized Gor'kov and Melik—Barkhudarov (GMB) approximation, we calculate the radio-frequency spectra of balanced and homogeneous ultracold Fermi gases within the framework of the non-self-consistent T-matrix approximation at unitarity in the normal phase. The corresponding equations are numerically calculated on the real frequency axis directly. It is found that our results agree well with the experimental result of the radio-frequency spectroscopy [Phys. Rev. Lett. 101 (2008) 140403].