The present study embeds the Immersed Boundary Method (IB method) in the 2D depth-averaged shallow water flow model being developed to solve the interior boundary problem in open channel. Two point and four point Dirac delta functions used in IB method were studied to examine their suitable equation. In addition, the effect caused by various ratios of IB marker’s gap to grid size were also analyzed. Two experimental cases, including cylinder pier and spur dike, were studied herein to demonstrate the practical applicability and limitation of IB method in fixed-bed and movable-bed open channel flow simulation.