With the advent of new high data rate wireless applications, as well as growth of existing wireless services, demand for additional spectrum is rapidly increasing. Existing "command-and-control" spectrum allocations defined by government regulatory authorities, such as federal communications commission (FCC), prohibit unlicensed access to licensed spectrum, constraining them instead to several heavily populated, interference-prone frequency bands. Though several report shows that still the spectrum is not utilized efficiently across time and frequency. To use spectrum efficiently, a new intelligent wireless communication system has been developed termed as cognitive radio network. Multi-carrier techniques, such as orthogonal frequency division multiplexing (OFDM) transceiver have a big role in such advance wireless standard. However an OFDM or NC-OFDM may have several subcarriers that are deactivated i.e. zero valued input that means many FFT calculations are there which are not required at all. So the hardware resources of the FFT are not fully being exploited. Therefore a new approach of FFT pruning algorithm has been very much required where several subcarriers are deactivated.