Abstract: Urban agglomeration has been one of the main space patterns of the urbanization process in China,which is the general product during the advancing stage of urbanization. Liaoning coastal urban agglomeration is the emergent in the structure system of Chinese urban agglomeration. Owing to advantaged location and development foundation, Liaoning coastal urban agglomeration in recent years has become the core region to promote the coastal development and revitalize the traditional industrial base of Northeast China. Based on comparative analysis on the relative concepts of urban agglomerations, this paper identifies the spatial extent of Liaoning coastal urban agglomeration according to the defined standards. Then it provides a research on structure characteristics of the urban agglomeration from polycentricity, function and network. The conclusions are as follows: first, both the population scale and density show significant characteristic of polycentricity, however, these two kinds of cores are not correspond with each other. The cores on the development axis of "Dalian-Yingkou-Panjin" are characterized by strong concentration, the ones on the east and west wings show the contrary characteristic. Second, the industrial function is in dominant position among the inter-regional division of labor but the productive services have not great influence on other regions. And the intra-regional industrial structure has great homogeneity while the service, transportation, commercial trade are complementary each other. Third, the transportation network is maturing and its system is forming. The intra-regional make close economic contacts with the transportation network. In a word, the point-axle spatial structure has been formed and developed towards network structure in Liaoning coastal urban agglomeration.