An improved method called spatial smoothing-criteria of information theory is presented based on W.Wax and T.Kailath's criteria of information theoretic used for estimation of the number of noncoherent sources. Compared to the WK's method，this improved one can be used to estimate the number of coherent sources and to raise estimating accuracy in case of high correlation，small-angle-separation or low SNR. The power spatial smoothing-information theoretic criteria method is also presented in order to obtain higher accuracy. Simulation results have been proved to be of the effectiveness of the improved method.