Rural tourism plays an irreplaceable important role in promoting targeted poverty alleviation, bridging the differences between urban and rural areas, stimulating the rural vitality and solving the issues on agriculture, countryside and farmers. So it is urgent to enhance efficient and intensive development of rural tourism. Under the new background about upgraded consumption environment, rural tourism increasingly becomes sophisticated, personalized, ecological and quality-oriented. At the same time, the tendency of rural tourism is inclined to the places with abundant resources, convenient transportation, high-distinctive space. Agglomeration development of rural tourism has become a significant feature in South Jiangsu. The paper analyzes different business entities about rural tourism and draws a conclusion that rural tourism attractions have a more obvious geographical cluster than festivals, but the differences between regions have been narrowed since 2005. What's more, the regional rural tourism cluster evolution presents a characteristic of dual constraint from the natural environment and the socio-economic performance. In the perspective of natural environment, with increasing distance from the waters and altitude elevation, the scale of rural tourism rapidly decreases and performs the rule of distance attenuation. The overall size of the main business presents a "peak-like" distribution in different dimensions of elevation. In the perspective of socio-economic performance, rural tourism cluster evolution performs a clear social and economic characteristic of the threshold requirement. Specifically, the urban population density of 10,000 people per km², grade highway density of 1000 meter per km², tourist spending density of 100,000 yuan per km², the disposable income density of 3 million yuan per km² are the optional rural tourism cluster space. Economic and social development, leisure and consumption growth are the fundamental driving force of rural tourism cluster. On the other hand, the evolution of rural tourism spatial structure presents diverse characteristics in South Jiangsu: rural tourism attractions show a multi-node network structure, and rural tourism festivals present dual-core with a satellite structure, while the evolution of rural tourism shows scattered hierarchy structure. Based on the above, in particular, to understand the spatial radiation effects of rural tourism spatial cluster evolution, the paper puts forward the view that rural tourism cluster is to boost the construction of rural tourism and ability and to make breakthroughs in building the holistic tourism destination, which may arouse heated discussions in academic fields.