In the radar system, the target estimation performance is affected not only by the measurement error such as the range or angle obtained from the radar but also by the placement of the radar, that is, the geometry. Accordingly, in this paper, we propose a optimal radar placement algorithm that minimizes the Cramer-Rao bound (CRB) by deriving the CRB for the target position in multiple monostatic radar systems with range and angle measurements. In addition, an averaged CRB concept was introduced to improve the estimation performance for successive trajectories. Simulation was performed and favorable results were obtained.