Abstract: Based on questionnaire survey and online travel notes, we obtained tourist flow data and used the social network theory and methods to build the model of cross-border tourism area network structure and the evaluation indices. The network structural index primarily measures core potential, core-periphery interaction and structural equivalence. The node structural index mainly measures centricity and structural hole. The boundary effect index estimates overall boundary effect and node boundary effect. From the perspective of tourist flow, the paper explores the tourism spatial network structure, node functional roles and the shielding effect of boundary by taking Lugu Lake in Sichuan and Yunnan as a case. It aims at enriching and deepening the thoughts of cross-border tourism research, developing a new approach for the study of network spatial structure and providing some scientific basis for the cross-border collaboration tourist areas. We conducted the survey in the Lugu Lake area during 12-24 August, 2012. We acquired background information through visiting tourism administration departments and major tourism companies and investigating the main tourism villages around the lake. We also interviewed visitors and ask them to fill out the questionnaires. The results show that: (1) the tourism spatial network of Lugu Lake is dense in the northern and central parts but sparse in the south, which shows a clear core-periphery structure. Tourist flows around the lake tend to choose circular and dotted routes. Influenced by the boundary effect, the overall network of tourist flow shows a boundary fracture phenomenon, while tourists in shared area show multicentric divergence. (2) The 15 tourism villages around the Lugu Lake can be divided into five types: core tourism site, sub-tourism center, important tourism node, general node and peripheral node. Same type of tourism nodes shows similar patterns in the centricity indicator. (3) There is a significant border effect in cross-border tourism activities. The shielding effect of Lugu Lake provincial administrative boundary is similar on both sides of the boundary, while the shielding effect of boundary nodes is remarkably different, with the proportion of nodes that have an obvious boundary effect significantly greater in Sichuan than Yunnan. (4) The spatial structure of cross-border tourism network in Lugu Lake is characterized by five levels of tourism bases, six travel axis, and three tourism systems. Considering this structure, some optimization paths are put forward, including building a Sichuan-Yunnan scenic area management committee to uniformly develop tourism resources and products, construct a unified brand, and jointly manage marketing; making use the function of the Xiaoluoshui and Dazu as cross-border tourist routes.

Key words: cross-border tourism, Lugu Lake, network structure and optimization, tourist flows