Abstract: Hierarchical structure is one of the main three structures in urban sy stem. Its characteristics can reflect the distribution patterns of cities in dif ferent scales and the degrees of concentration or dispersion of urban population , and also, can help us to understand the development stage of urban system. By using the theories and methods of urban primacy index, fractal, and urban gravit y transfer, the hierarchical structure of urban system in the multi-cities of c entral Liaoning were analyzed. The results showed that the multi-cities of cent ral Liaoning had a fractal hierarchical structure, their sizes were in primacy d istribution, and middle-size cities were fewer. The spatial distribution of cit y size tended to balance, but the development process had significant regional d ifference. From 1982 to 2005, the gravity of urban population had an overall sou thwestward transfer.

Key words: Sulphur, Heavy metals, Concentration, Dynamic, Growth ring set, Pinus taiwanensis