Large eddy simulation for granular-fluid in sheet-flow regime under oscillatory flow has been performed by using the solid-liquid two-phase flow model based on the Euler-Lagrange coupling. Rheological characteristics of sheet-flow layer where frequent inter-granular collisions occur has been investigated computationally. The simulated particle system is verified by comparison with the previous experimental results. Then the transitional area in the sheet-flow layer satisfying Bagnold's law is highlighted. And active inter-granular collisions are found by decreasing of the period of oscillation under the same bottom shear stress condition.