This paper is studied to the performance characteristics and the flow behavior of multi-blade fan according to blade-end open-ratio (k) of near the shroud side. Firstly, the properties related to performance of the fan have been measured in a test rig. In the next, numerical calculations are conducted to explain the complex, three-dimensional flow behavior and performance of the fan using CFX 12.0 commercial code. The validation of numerical results has been performed in comparison with the experimental results. The numerical results provide a comprehensive understanding of the flow behavior inside the fan. By changing the open ratio of blade-end near the shroud side, the flow behavior and inactive zone is respectively different. The separated flows are strongly occurred in a blade passage and the inactive zones are formed near the shroud as k = 0 and 20% cases, relatively. The flow separation and inactive zone reduce fan's efficiency because they cause internal loss. The best efficiency and flow behavior of the fan is appeared to be at k = 70% case. According to open ratio of blade-end near shroud side, the flow behavior can be changed and the efficiency of a fan can be increasing. The objective of this study is to understand of the complex flow behavior inside the fan and offer guidance for fan designing.