The 15^th Tri-University International Joint Seminar & Symposium provides a forum for students, scientists and Engineers to discuss on the following topics: (1)Population, (2)Food, (3)Energy, (4)Environment, and (5)Ecological Development. These topics are deeply related to each other and are all important for the sustainable，harmonic development and the survival of human beings. Agriculture and technology based on the engineering are the keys, and they must play necessarily an important role for a more improved situation leading to the future. This is a very good opportunity to promote the mutual understanding of these universities in preparing the countermeasures of the forthcoming era.