This paper is an attempt to understand the variations of spatial distribution of population within the town of Ta-his, a 200 years old small town. The time period of this analysis is from 1905 to 1985, while the spatial concentration of population and urbanization in Taiwan Area during this period has already been developing. The basic indexes of analysis are average growth rate of population, rate of natural increase, rate of social increase and rate of net migration annually. The source of basic data of population are from the demographic fact books in Taiwan Area, which is published by the Japanese colonial government and the ministry of interior of the Republic of China through the years. The basic area-unit of this analysis are all Lis, which is the smallest statistical unit in Taiwan that cover the entire Ta-hsi. The result of this research is summarized as follows: 1. The variations of spatial distribution within the town of Ta-hsi through the years reflect the changes of the town’s function and the natural deviding line of the River Ta-han generally. 2. According to the analysis, it has been found that during the period before the mid 1950's, the areas of dense population and rapid population growth are concentrated on the Eastern Region (the eastern part of River Ta-han) which traditionally is the economic center of this town. But during the period after the mid 1950's, the velocity of population growth in the Western Region (the western part of the river) which is an industrial region at recent times was much faster than the Eastern Region. This change helped to form two core centers of population distribution in Ta-hsi for present times. 3. The most important factor of the difference of population growth between the two regions at two periods is the change of migration. Before the mid 1950’s, the net in-migration rate in the Eastern Region is more than the region of west. Nevertheless, the net in-migration rate in the Eastern Region during the period after the mid 1950's is less than the region of west. 4. There was evident difference between two regions on the sources of net in-migration. The sources of net in-migration in the Eastern Region mostly came from the migration between Lis within the town and the sources of net in-migration in the Western Region are essentially based on the in-migration came from the outside.