In this paper, we consider computationally efficient direction of arrival (DOA) estimation for monistatic multiple-input multiple-output (MIMO) array. The computational loads of the propagator method (PM) can be significantly smaller since the PM does not require any eigen-value decomposition of the cross correlation matrix and singular value decomposition of the received data. DOA estimation for the MIMO array using PM and reduced-dimension transformation is proposed, and the proposed algorithm has less computational complexity than PM. The proposed algorithm works well without spectrum searching. Furthermore, the proposed algorithm still has slightly angle estimation performance than PM. The variance of the estimation error and Cramér-Rao Bound (CRB) of DOA estimation are derived. Simulation results verify the usefulness of the proposed algorithm.