When trees were living, tress usually injured by climate change, lightning damage, wind damage, plant diseases, insect pests and human being, etc. Therefore, trees needed strengthening conservation to keep trees healthy. The purposes of this courses is using nondestructive technique to understanding healthy of trees and monitoring tree health. A variety of tools, equipment and techniques have been developed to evaluate tree stability. To assessment the risk of tree. Generally, we could use visual methods to determine situation of tree growth characters, plant diseases and insect pests. If considering the risk of trees, we usually assessment the trunk internal material, It will help us to make sure the difference of nondestructive technology to assessment the material strength and risk assessment of a tree and providing the protection measures, compensation and appropriate treatment.