溪頭營林區屬臺大實驗林所經營之國有林班地，轄有一至六等林班。總面積2,488公頃，海拔在600公尺至2025公尺。區內四面環山，中央為凹地，有一北勢溪。本區年平均溫度20.5℃，雨量集中在5-9月間，年平均雨量為2,614mm，為夏雨型氣候。經過一年期間之野外調查與陰棚栽培，並參考往昔研究之文獻和資料，本研究共收錄溪頭營林區之蘭科植物43屬92種，包含39種為地生型、44種為附生型、9種為腐生蘭等3種生活型，其中特有種有18種。另除收集植物之分布、產地、花期與族群生育情形外，並同時調查各植物之生育地環境以及附近植物群落之類型，以便對蘭科植物之群落加以研判。並依據IUCN(2003)瀕危物種紅色名錄及保護區的具體情況對其瀕危等級進行評估，計列出75種值得保護之蘭科植物，包括稀有植物9種與易危植物(生存後威脅) 66種。由於溪頭獨特的地理和氣候條件，蘭科植物的附生與地生種類數目有大致相同的特點。如此豐富而寶貴的蘭科植物資源迫切需要制定出一個全面的保護策略以及採取可行的保護措施來進行保護，同時需對溪頭營林區內蘭科植物進行長期監測與研究，俾提供基礎性的數據。

Wild species of Orchid family are considered as a key group for plant conservation. The Xitou Tract, located at the Alishan mountains in central Taiwan, belongs to Compartment 1-6, Experimental Forest, College of Bio-Resources and Agriculture, National Taiwan University. The elevations range from 600 to 2,025m. The reserve area is about 2,488 ha. The orchid species, individual numbers, their life forms and habitat conditions were surveyed. Their floristic components were analyzed and their endangerment degrees were evaluated according to the IUCN Red List Categories and Criteria. We recorded 92 orchid species from 43 genera in total, including 39 terrestrial orchid species, 44 epiphytic orchid species, 9 saprophytic orchids, and 18 endemic species. Xitou Tract has rich orchid resources with the number of terrestrial orchid species similar to that of epiphytic orchids. We believe our results could supply basic data for generating specific management strategies, long term monitoring and study of orchids in Xitou Tract.