The Borneo black sweet Coelogyne Pandurata is one of the mascots of flora in East Kalimantan Tropical Rainforest. This orchid species only grows on the Borneo. The uniqueness of The Borneo black orchid Coelogyne Pandurata, has a black tongue (labellum) with a few green and hairy stripes. This research is to develop an expert system for identifying pests and diseases of black orchids, as a support for the conservation of biodiversity in the East Kalimantan tropical rainforests. The expert system is equipped with a knowledge base in diagnosing pests, symptoms, and diseases of black orchid using Bayes theorem. In this research 4 pests disturbed black orchids, namely bare snail pests, caterpillars pests, grasshoppers pests, and ant pests. The diseases that attacked black orchids were obtained, namely brown spot disease, fusarium wilt disease, soft rot disease, and root rot disease. The result of the calculation of the Bayes Theorem based on 5 symptoms chosen by the user that black orchid has a 40% chance of experiencing root rot disease.