穿洞形成于溶蚀发育的洞穴，是已脱离地下水位、高悬于山体上部、两端为开口状的残留溶洞通道。洞壁常有边槽、流痕、贝窝等形态，洞体呈通道式，是流水岩溶的一种标志性形态。东兰国家地质公园有大量穿洞，如著名的月亮山穿洞、天宝山穿洞等。

Karst cave is formed in the cave where dissolution develops and it is an open residual cave passage that has been separated from the underground water level and was hanged above the top of the mountain. On the cave wall, there exists notch, flow mark, flute and other shapes. The body of the cave shaped like a channel, which is a typical form of fluvial karst. There are a large number of karst caves in Donglan National Geopark,such as famous Tianbaoshan and Moon mountain karst cave.