In this paper, the problem of direction-of-arrival (DOA) estimation of quasi-stationary signals (QSS) in uniform linear arrays (ULAs) with unknown mutual coupling is considered. By taking advantage of the quasi-stationarity of signals and the special structure of mutual coupling matrix (MCM) of ULAs, a computational efficient algorithm is devised to determine the DOAs. Different from the existing approaches for DOA estimation with unknown mutual coupling, the proposed method can simultaneously enjoy various superiorities including: 1) it is computationally efficient without the need of spectral search, 2) it can resolve more sources, and 3) it is robust against unknown noise. Simulations are conducted to demonstrate the effectiveness and superiority of the proposed DOA estimator.