Mobile wireless communications at high speeds are rapidly growing in popularity. Orthogonal frequency division multiplexing(OFDM) technology will emerge as a key technology for wireless communication systems to achieve spectral efficiency and high data capacity. A 4G communication system uses OFDM modulation. OFDM is a crucial enabling technology for wireless communication systems, both present and future. Various references have been used to establish a mathematical model of the performances of OFDM systems based on some factors. OFDM demonstrates high performance and is very tolerable to multipath delays and channel noise. We analyze the performance of OFDM in this paper based on power spectral density(PSD), spectral efficiency, signal- to-noise ratio(SNR), and bit error rate(BER).