In this paper, the estimation of angular difference between adjacent sources is investigated in the uniform linear array. In the presence of additive Gaussian noise, we use singular value decomposition to obtain the eigenvalues of the spatial covariance matrix. Thus, the expressions of eigenvalues related to the signal are obtained. The smaller one between the eigenvalues is related to the degree of difference between the two sources and we derive the expression of the angular difference estimation through it. In practice, the more samples observed, the more accurate the estimate is. Numerical results confirm our theoretical analysis and demonstrate the effectiveness of the proposed estimation method. The result in this paper has important guiding significance for array signal processing in the actual environment.