Abstract: A Carrier Frequency Offset (CFO) estimation method is proposed based on signal detection in Superposition Coded Modulation (SCM)-OFDM systems. This method reconstructs first the received signal by decision symbols from the SCM iterative detector, and then estimates the CFO by employing the Minimum Mean Squared Error (MMSE) criterion. It is an efficient blind CFO estimation method without the aid of extra training sequences or pilot symbols. Furthermore, an improved method is proposed to estimate CFO in this paper. In the improved method, a joint CFO estimation and signal detection receiver is realized by an iterative process. Thus data detection and CFO estimation need to be implemented in each iteration process. And the receiver can compensate the CFO by the last estimated value during signal detection. Simulation results show that the proposed CFO estimation methods can significantly and accurately estimate the CFO for SCM-OFDM systems.