This paper probe into and study on the theoretic basis of ecosystem monitoring, evaluation and adjustment along the border of Yunnan Province, using the theory of Global Millennium Ecosystem Assessment. The key points are whether ecosystem can be effectively monitored and adjusted, which features can be identified and monitored by 3S technologies, and in what spatial and temporal dimension they can be monitored and adjusted. Secondly, the method and key technology, including the setup of method & technology system, building of index system, multi-dimension effect and dimension transformation, mathematic model building, and controlling & adjustment mode and decision making, etc., were researched. Thirdly, in case study section, the background database was built, and then large, medium and small dimension sample areas were used in current situation assessment for the whole region, impact assessment for major riverbed, typical road sector and key ports, and forecasting for the border region, respectively. At last, comprehensive controlling and adjustment mode and scheme were made up, and the research results was displayed in dynamically and virtually. From these research activities we got some conclusions, i.e., at first, the study on the theory, method and technology of 3S based ecosystem monitoring, assessment and adjustment, is an important contribution to ecological-environment issues along mainland border of China; secondly, trans-boundary ecological-environment is an item which can be monitored, evaluated and adjusted using 3S technologies which are the most suitable ones extending and strengthening human being’s ability of perception and procession to the nature. Fourthly, what we had done in this field is the beginning for our group, further work will be done deeply and widely.