In MIMO (Multiple Input Multiple Output) radar systems multiple antennas at transmit and receive sides are used to improve the detection performance. Two important parameters which have an effect on the coverage and performance of these systems are: the transmitters’ power and the receivers’ positions. In this paper, assuming the Rayleigh scatter model for the target, the probability of detection is obtained for a MIMO radar system, by designing the Neyman-Pearson detector. Then, an iterative procedure is proposed for appropriate positioning of the receive antennas’, such that this probability of detection is improved. Finally, the transmitters’ powers are determined based on the gradient descent algorithm.