Abstract: Peak-to-average power ratio of orthogonal frequency division multiplexing signals is analyzed when the sampling rate is different. The samples according to Nyquist sample rate in one period of OFDM symbol are independent identically distributed random variables. When oversampling factor is 2, the covariance matrix composed of the coefficients of correlation between those samples can be calculated by numerical method. As a result, all samples in one symbol are approximately independent when oversampling factor is 2. So the probability distribution function of peak-to-average power ratio can be achieved. The results are proved by simulation.