In the wireless technologies there was an Exponential growth in the number of wireless subscribers and continuous demand for high data rates, where radio frequency spectrum is becoming increasingly crowded. To overcome this kind of circumstances spectrum sensing in cognitive radio networks is becoming more important to current and future wireless communication system to identify underutilized spectrum with characterizing interference and hence achieving reliable and efficient operation. In this paper Energy detection and Matched filter based spectrum sensing is discussed in detail. The performance analysis of Energy Detection and Matched filter detection over a Rayleigh fading channel evaluated through Receiver operating characteristic curve with Probability of detection Vs Probability of False alarm.