A series of experiments have been performed to investigate the premixed flame behavior during its propagation in a rectangle chamber with various obstacles mounted on its wall. A high speed shadow-graph system was used to visualize the flame front development. Three different obstacles were used, and their corresponding sequential images are presented and used to quantity the shape and location of the flame front during its propagation. Our experimental results for flame acceleration showed similar results as the literature, the flame accelerates as it passes over the obstacles and then decelerates due to the existence of a recirculation zone behind the obstacles. However. significant changes in flame structures and turbulent transitions were found for the three different obstacles. It is found that the passage, which is composed of the surface shape of the obstacle and the inner wall of chamber; is critical to the shape of the flame front and propagation of the flame. The obstacle with the largest volume results in the fastest flame acceleration.