Abstract: In normalization design of complex object schemes, the semantic relationships among objects play an important role. But there is no research on it. Some properties of a set of object dependencies are discussed in this paper. First summarized are some basic concepts and properties about object dependency （OD）, key, and reduced OD. Then, algorithm JINGSI producing all keys with respect to a set of ODs is given and proved. Finally, the properties for the set of ODs as the input for normalization design of complex object schemes are shown, and based on it normalization design for complex object schemes is improved.