The problem of joint direction of arrival (DOA) and Doppler frequency estimation of coherent targets in a monostatic multiple-input multiple-output (MIMO) radar is addressed. Based on the propagator method (PM), an RD-FSS-PM algorithm is proposed, which can effectively estimate the DOA and Doppler frequency of coherent targets with low computational load. In the RD-FSS-PM algorithm, we firstly perform a reduced-dimension (RD) transformation on received signals to decrease the computational load, then use forward spatial smoothing (FSS) to decorrelate the coherent signals and apply the PM to estimate the DOA and Doppler frequency simultaneously, which are automatically paired. Compared with the conventional FSS-PM method, the RD-FSS-PM algorithm has much better DOA estimation performance, very close frequency estimation accuracy and much less complexity. The variance of the estimation error and the Cramer-Rao bound (CRB) of the DOA and frequency estimation are derived. Simulation results are presented to show the effectiveness and improvement of the new approach.