Since 1992, Green Earth Network（GEN） has been continuing tree-planting cooperation in the villages in Datong, Shanxi, China, which belongs to Huangtu Plateau. We planted 18.8 million trees spreading 5,600 ha in cooperation with local people. Through failures in early stages, we accumulated technique and experience, then we succeeded and some of the projects became a model of tree planting. This area suffered seriously during World War II. The feeling toward Japan was very bad. While dispatching 150-250 volunteers every year and planting trees together, a mutual understanding deepened. When the Great East Japan Earthquake occurred, much donation was sent from many villages. Japan can live and go only in a good relationship with Asian nations. In order to deepen mutual understanding, the most certain way is to cooperate toward a common target. GEN thinks environmental cooperation is the best field. We want to find out the direction that we should go to through looking back the experiences in both Japan and China. It should contain some good lessons for the people of the different places tackling the different problems.