The potential initiation of debris flow after outbreak of an earthquake is widely concerned by the society. This paper aims at investigating on initiation of loose gravelly clay deposit after earthquake using seepage and general limit equilibrium coupled method. The study area is the source area of debris flow in Weijia River basin, Wenchuan, Southwestern China where series of debris flows occurred after the May 12th 2008 Wenchuan Earthquake. A simplified model of gravelly clay slope under different consolidate durations and rainfall intensities was simulated using finite element method. The pore water pressure distributions in the slope at different consolidate durations were obtained by seepage analysis. And the stability of the slopes with different consolidate durations under different rainfall intensities were analyzed. The results show that the consolidation of gravelly clay deposit after an earthquake has a considerable influence on the shear strength index and the permeability coefficient of the loose deposit at earthquake area. The pore water pressures and hydraulic gradient at outflow point of the slope toe increase with the increase in the consolidate duration of the slope soil. The minimum factor of safety or the stability of gravelly clay slope decreases with the increase in the consolidate duration of loose deposit soil within the tested three years which suggest that the consolidation and changes in permeability and strength of loose deposit soil increases the potential of initiation of debris flow in the earthquake affected area during the period.