Due to waveguide dispersion and array shape distortion, target's energy spreads in the vicinity of direction of arrival in spatial orientation spectrum. To solve this problem, a spatial spectrum estimation method using beam signal spectral decomposition is proposed. Utilizing correlation between signals which spread in multiple beams, beam signal spectrum is decomposed using singular value decomposition to achieve coherent signal accumulation. Maximum eigenvalue is extracted as output energy of the intermediate beam. Without the need of estimating array shape, output gain of spatial energy spectrum is increased.