A method for blind detection of OFDM signal based on power spectrum reprocessing is presented for distinguishing OFDM signal and single carrier modulation signals. The method takes full advantage of cryptic period of OFDM signal and enhances its ability for processing through power spectrum pretreatment, and has strong ability to suppress additive interference and is applicable to frequency selectivity fading channel and accurately estimate subcarrier frequency interval, symbol period, signal bandwidth and subcarrier number of OFDM signal. The simulation result shows that the new method is able to detect OFDM signals rapidly and accurately in condition of relatively low signal-noise ratio, and achieves high identification probability, has high adaptability for frequency selectivity fading channel, and has also low computational complexity, high precision, and is suitable for hardware implement.