Guangao and Jupen Mountain areas are General Control Areas in the northwestern part of Yushan National Park. Most of biological resource surveys of these two areas were conducted before 1993. The purposes of this study were to investigate the biodiversity of these two areas and identify changes over the past 20 years in the quality and quantity of various taxa. This information is necessary to re-evaluate the management category of these areas. In 2009, at Guangao area along Jyunda Logging Road between 65 km and 69 km, we set up research plots to study plant species diversity, analyze vegetation, and survey for bird species and density, for mammal diversity, and for invertebrates, including insects and snails. We surveyed the upstream area of the Juynda River near the Wushuang Swinging Bridge and along the hiking trail to Jupen Mountain. In the Guangao area (about 6 km2), we recorded 78 vascular plant species, 42 bird species (including 10 protected species), 27 mammal species (including 6 protected species), 256 insect species (including 2 protected species), and 29 snail species. Although the Guangao area was severely disturbed by logging activities in the past, its ecosystem is now in the primary stages of succession into forest.