Abstract: Panlongdong Cave,located at Huangyan county of Zhejiang Proveince,is a large-scale underground cave group left by ancient quarrying,and has been explored to be Jinxiu-Huangyan scenery site.Indicated by practical measurements,the No.3 cave of the cave group is up to the height of 64.3m,which is the highest one of known large-scale ancient underground projects in the world.In the present paper,the authors analyze possible reasons of the ancient project maintaining several hundred years of stability,and discover some ancient simple scientific ideas and lofty quarrying techniques contained in this ancient project.