There are almost a hundred people coming from forty universities and dozens of scientific institutions collaborating with our researchers every year. Every year we hold more than twenty lunch seminars, special forums on the edge of science and cross-disciplinary subjects and more than a hundred times of special topic talks. We organize several international conferences every year, and we jointly organized the international conference on string theory in 2006. There were 350 foreigners attending the meeting. We jointly held the summer school on complicated systems several times with the American Santa Fe research center since 2005. The ITP has received many Nobel Prize winners visit and we received American Secretary of State’s science adviser twice in 2006 and 2007 respectively. All these collaboration activities stimulate more and more young researchers to join the academic exchange, and helps our young scientists to learn more about the international and domestic scientific development trends, and therefore able to contribute to the development of the ITP and theoretical physics of our country.