Abstract: Using the acaricidal activity to guide the isolation，the compound Ⅳ，which had the highest contact and systemic toxicity to Tetranychus cinnabarinus，was obtained from ethyl acetate extracts of roots of Stellera chamaejasme L. The structure of compound Ⅳ was established as scopoletin by analysis of NMR（1H NMR，13C NMR）and IR data. The results of acaricidal activity analysis showed that scopoletin may be the principal acaricidal substance in the ethyl acetate extracts of S. chamaejasme extracts. And the mean lethal concentrations（LC50）of scopoletin for contact and systemic toxicity were 1.267 and 7.388 mg · mL-1，respectively. Subsequently，compound Ⅳ was analyzed by NMR and IR methods，and its contact and systemic toxicity to mites were determined. In accordance with the spectral data（1H NMR，13C NMR and IR）of compound Ⅳ，the chemical compound was identified as scopoletin. Scopoletin may be the principal acaricidal substance in S. chamaejasme extracts. And the mean lethal concentrations（LC50）of scopoletin for contact and systemic toxicity were 1.267 and 7.388 mg · mL-1，respectively.

Key words: Stellera chamaejasme, acaricidal activity, Tetranychus cinnabarinus, scopoletin