The characteristics of pedestrian movement down stairs from high-rise building influence the total evacuation time, the formation of congestion and even the safety of evacuees. In this paper two different experimental scenarios, which could be regarded as the phased evacuation and total evacuation respectively, were conducted on stairs in a high-rise building to investigate the evacuation process and pedestrian movement characteristics down stairs. The evacuation processes were recorded by video cameras, and the movement parameters were extracted from the video data. In experimental scenario one and two, the space-time distribution, the speed of participants walking through two adjacent floors and specific flow for participants through different stair landings were analyzed and discussed. Then, the fundamental diagrams for pedestrians in the two different evacuation scenarios were presented followed by the analysis of the influences of merging flow on pedestrian movement. It is found that the longer time intervals between participants occur because of the bottlenecks caused by slow movement individuals in experimental scenario one. In experimental scenario two, it is found that participants who stand in front of the queue accelerate just before the merging with participants coming from upstairs. Moreover, from the analysis of the fundamental diagram, we find that the merging flow influences pedestrians' movement down stairs, and the detailed egress facilities and evacuation processes should be taken into account when the functions of SFPE Handbook are used to predict the evacuation variables. It is also found that the speeds of participants from upstairs are reduced by the entry of participants from the corresponding floors during the merging time period.