The aims of this paper are to identify information interaction patterns among the 30 major cities of China, and to extract centralization fields and decentralization fields which are defined as influenced regions of information centralization and decentralization flows.Data for this analysis are long distance telephone call data taken from the National Post Bureau. The data are expressed in the form of 30 ?30 origin-destination flow matrix. R-mode and Q-mode factor analyses were employed to reduce the matrix to its underlying fields. The results are as follows:1. There are a few centralization fields and decentralization fields in which both of the first fields are much stronger than others (Fig. 1 and Fig. 2).2. The hierarchical structure of cores which make centralizing and decentralizing is in the form of 1:1:6.The first-order core is Beijing.The second-order is Shanghai. The third-order consists of Tianjin, Guangzhou, Nanjing, Xian, Shenyang, and Wuhan.3. There is no contract between the same order cores.All of the cities directly contract to Beijing, and a few of them also to Shanghai (Fig. 1 and Fig. 2).4. The regional patterns of the fields show all of first-order and second-order cores, and most of third-order cores are located in the eastern coastal region.5. The pattern of information interaction is mainly caused by the central-power administration system, some by inter-city economic contracts.A planning of the information interaction pattern has been devised on the basis of the above analysis. The main points are as follows (Fig. 3):1. A strong economic information centralization and decentralization fields must be constructed whose core is located in Shanghai, and its order will rise to the same as Beijing.2. The six third-order cores should be developed, and be raised as second-order cores.3. The "three steps" regional pattern will be formed in which all of first-order cores and most of second-order cores will be located in the rich coastal region, other second-order cores in inland, and no core in the poor peripherical region.4. The contracts should be encouraged between the same-order cores and between the different-order cores.