The present study utilized non-invasive enzyme-linked immunosorbent assays（ELISA） to measure the changes of fecal reproductive steroids in 6 Formosan black bears （Ursus thibetanus formosanus）at the Low Altitude Experimental Station of Endemic Species Research Institute. The results indicated Formosan black bears were seasonal breeder and the major breeding season was between March and June. Testosterone concentrations were fluctuated according to seasonal changes. The concentrations increased in late winter and reached to the highest peak in spring. Relatively regular patterns of estradiol and progesterone concentrations in pregnancy were observed in parturient females, and the gestation periods were about 6 to 7.5 months. Because the gestation periods were different, it might include a special reproductive phenomenon, delayed implantation of embryo. Moreover, female Formosan black bears have hibernated behaviors, such as, fasting, non-excretion and sluggish activity at about a period before and after parturition. In non-mated females, progesterone concentrations were irregular and the peaks were lower than the mated bears. Health condition and environmental factors influences caused different reproductive behaviors in each individual. Thus, testosterone and estradiol concentrations were not the only factor that had influenced on mating behavior. The annual pattern could be divided into an active and like-hibernate period. Because of well climate and abundant food, the annual pattern did not include hibernation. This study provides useful information for the wildlife research and management of the Formosan black bears. Furthermore, the present study could also contribute to the conservation of Taiwanese biodiversity.