Cyclic delay diversity (CDD) is a simple technique to intentionally increase frequency selectivity of channels for orthogonal frequency division multiplexing (OFDM). This letter evaluates the performance of post-FFT fine frequency estimation scheme for OFDM-based FM system using CDD. A new and accurate mean square error expression of the fine frequency estimator is derived in the CDD-based OFDM system, and simulation results are provided to verify our analysis.