This paper investigates the dynamic angle of repose underneath the submarine pipeline. Using a sand deposition model, the analysis of forces acting on non-cohesive sand particle gives the formulas of dynamic angle of repose in the scour hole. The formulas for different scenarios are discussed and it is observed that the angle upstream the vertical axis of the pipe increases with the increase of sand Reynolds number. The angle downstream, however, shows a contrary trend. Besides, the angle upstream is bigger than that downstream. The comparison of the calculation results with the experimental data indicates that the formula predicts the angle of scour hole under a pipeline reasonably well.