Orchids is one of biggest biodiversity in Borneo. The presence of orchid in nature also indicate the stabile ecosystem. But, because the potential of orchids as the ornamental plant, the exsistinct of them is threatened. So, the aim of this study is to analyse the species diversity indext and habitat preferences of orchid in Tarakan forest. the method of this study was a survey by exploring the forest of Tarakan Orchid Garden area. The environmental parameters of each recorded orchid is measured, they are light instensity, altitude, temperature, and humidity. The orchid species that have been identified are then searched for the value of the important index of species diversity using Shannon-Winner equation. The study revealed that there were 6 species of orchids (Cattleya luteola, Catasetum sp., Bulbophylum phaleoanopsis, Bromheadia sp., Bromheadia finlaysoniana, Dendrobium anosmum) in research location. The biodiversity indext for 6 orchid was in low category with average value 0.1998. Researcher recorded that there were two types of habitat preferences of orchid in research area, namely epiphytic and terrestrial. The balance of all environmental parameters that measured are strongly affected the orchid diversity and growth.