Abstract: The abundant forest resources in Taiwan contain plenty of natural products with medicinal or healthy functions. Extraction of natural compounds having specific bioactivies and/or medicinal properties from plants is one of the important developments of natural products researches. Many natural products existed in the endemic plants are of great potential as bioactive agents or pharmaceuticals. Researches and developments in natural products from native plants in Taiwan are worthy to further exploration. Michelia formosana is a native plant, the first class of hardwoods and also one of the five precious hardwoods in Taiwan. The antifungal activity of M. formosana wood is commendable. In addition, M. formosana tree possesses the efficacy against pest insects and pathogenic fungi. Therefore, the objectives of this project are to evaluate the mosquitocidal and acaricidal activities of M. formosana extracts and isolate compounds possessed these two activities from M. formosana. The extracts are separated into several subfractions by liquid-liquid partitions, and every subfractions collected are under the examination for bioactivity. The pure compounds existed in the subfractions are finally isolated by chromatographic techniques and identified by modern spectroscopic analyses. Identified compounds are also examined with assays to confirm their mosquitocidal and acaricidal activities. The influences of extractives on pesticides of mosquito larvae and dust mites are analyzed and the mechanisms of inhibition actions are also investigated. Through this research, it is expected that mosquitocidal and acaricidal compounds isolated from M. formosana be of great potential as natural environmental pesticides. This work would be helpful to provide the utilization of forest products for environmentally friendly pesticides.