Debris flows caused by heavy rainfall occur along long watersheds and travel at extremely rapid velocity. These debris flows can impact large areas and often cause economic and societal damages. For this reason, barriers against debris flows have been widely constructed. In particular, slit-type barriers are popularly used because of the minimum environmental disturbance. However, the performance of such slit-type barriers is not fully understood. This paper explores roles of spacing and angle of slit-type barriers on velocity reduction of debris flows. The scaled physical modeling experiments were performed to identify reduction of debris velocity and to assess the performance of debris flow barriers. The results indicate that the performance of barriers is heavily affected by spacing between slit-type barriers and angle of barriers from flow direction.