In this paper, we consider the Multiple Input Multiple Output (MIMO) - cooperative spectrum sensing based on Energy detection in cognitive radio networks. The primary user data is forwarded to the fusion center with N receiving antennas through the K cognitive radio user each with M transmitting antennas using Time division multiple access (TDMA). The network is operating over independent and identically distributed (IID) Rayleigh fading channel. We obtain the probability density function of soft combined signal from K cognitive users. We arrived an expression for average detection probability by using an alternate of generalized Marcum Q-function and compared the performance of different soft combining schemes under various MIMO systems by simulation. © 2013 IEEE.