The demand for high speed applications are growing at a faster rate. To meet these requirements, 4G technologies are being used nowadays. COFDM based WiMax is the outcome in this direction which promises to cater these high speed and high quality applications. Worldwide Interoperability for Microwave Access (WiMax) is an IEEE 802.16 standard-based broadband wireless access (BWA) technology which employs Coded orthogonal frequency division multiplexing access (COFDM). This paper analyses Bit Error Rate for WiMax based COFDM system with BPSK under various channel conditions like AWGN, Rayleigh, Rician and Nakagami. Further, Rayleigh and Rician channels are investigated in detail. It has been observed that performance of Nakagami fading channel is better than other fading channels.