In this paper, a performance analysis of amplify and forward (AF) relaying cooperative diversity system with relay selection is given when all terminals are moving. We have derived analytical expressions for probability density function (PDF), cumulative distribution function (CDF) and moment generating function (MGF) of end to end signal to noise ratio (SNR) for the considered system. Then, the symbol error rate performance (SER) of the system is calculated for MPSK modulation assuming the all links have double Rayleigh distribution.