The research of the spatio-temporal evolution discipline of tourist flow helped to reveal inter-functional course and mechanism in terms of each inner-element of tourism system, and also provided bases for tourism planning, product development, as well as marketing and tourism management. This paper adopted K-Means cluster to undertake spatio-temporal analysis of the number of tourists in Yancheng eco-tourism area for David's deer. The phrases and market division of tourist changes in eco-tourism area for David's deer were discussed from two scales, namely, inner-provincial and inter-provincial.The results showed that the tourist flow of the above-mentioned two scales could be divided into three stages between 1998 and 2005, and could be marked off four different types of customer market properly. Yancheng eco-tourism area for David's deer ought to ascertain its target market and the management strategy according to the spatio-temporal distribution characteristics of the tourist flow. The most important core tourist markets of this eco-tourism area were the fourth and the third kinds of customer market, namely, Yancheng and Nanjing city in Jiangsu Province. When it comes to domestic tourist market, the priority should be given to the fourth one—Jiangzhehu area—as the basic market to explore. Temporal characteristics of tourist flow in different stages indicated that the tourist market of Yancheng eco-tourism area for David's deer varied amid relative stability, and represented distinctive regional difference. Except effects of space distance and transportation, the diversification of tourist flow was closely related with economic development, tourist motivation and choice, as well as theme tourism activities and tourism promotion. The pressing task for eco-tourism area was how to protect its resources and environment. The increase of tourists couldn't be pursued simply. We should attach importance to the optimization of tourism market structure, and select tourist market that would be highly responsible for environmental protection in order to pursue connotative development. Owing to the trend that the tourist market concentrated on Jiangzhehu area, in short term we could give the priority to explore the above-mentioned market (especially the tourist market in southern Jiangsu and Shanghai), and provide tourism and service products to meet the demands of tourist market. However, in the long term, in the precondition of proper eco-resource and environmental protection, the tourist market should be exploited vigorously and the convergence of tourist market should be dispersed further though effective integration and deep exploration of eco-tourism products in Yancheng seashore to attract tourists with high quality on a larger scale. The research finding showed that K-Means cluster could indicate the detailed information of spatio-temporal evolution in terms of tourist market and could be regarded as an effective analysis method for the spatio-temporal distribution and evolution characteristics.