Abstract: A new DOA estimation algorithm called SPOC(spatial processing——optimized and constrained) which is based on MAP(maximum a posteriori) criterion is introduced.In the algorithm the spatial energy received by array is divided into a large number of uniformly spaced cells,each of which is assumed to be transmitted by a point source.Maximum a posteriori criterion is used in the algorithm,which minimize the total power received while maintain the signal power received in the desired direction.The DOA estimation is accomplished by estimating each of the point source’s energy.The algorithm avoids estimation errors caused by target movement or non-stationarity of environment by using single snapshot.In this paper,diagonal loading approach is used to enhance the stability of the algorithm in low SNR(signal to noise ratio).An experiment is taken in a water tank by using only one transducer and one receiver.The experiment shows that DL-SPOC has higher angular resolution than other algorithms such as CBF and MVDR.