An antenna geometry design method of Multiple-Input Multiple-Output(MIMO) radar based on D-optimality Criterion(DOBC) is proposed in order to minimize Mean Square Error(MSE) of the estimations. Firstly, the constraints of DOBC designs are derived; then, the sensitivity properties of the DOBC designs are analyzed, which are only affected by the separation of the targets and are independent of the azimuth of targets; the Cramer-Rao Lower Bound(CRLB) of the estimations in the far field condition is also deduced. DOBC criteria can be looked as the modified CRLB and provides a tighter bound for performance measure of the Maximum Likelihood Estimate(MLE) algorithm. Simulation results demonstrate that compared with minimum redundancy arrays and uniform arrays, DOBC designs have better performance in parameter estimation. Furthermore, it is not restricted by the array aperture. As the aperture increases, the resolution will be improved and the spurious peaks will become higher at the same time, which will result in a very large error in the DOA estimation with low SNR. Therefore, an appropriate aperture must be chosen according to the physical requirements.