Abstract: The model of pilot symbols assisted modulation adaptive modulation orthogonal frequehcy division multiplexing system is given in Rayleigh fading。Based on this model, spectral efficiency definition and calculation are analyzed. According to bit error rate of PSAM OFDM, the numerical result is presented under specific channel model. In order to be reference for practical system design, the result shows influences of receiver non-ideal channel estimation and system overhead must be considered.