OBJECTIVE：To extract and identify the volatile components of the roots of Polyalthia nemoralis，and to evaluate its biological activity in vitro. METHODS：Supercritical CO2 extraction（SFE-CO2）was performed to extract volatile compounds from the roots of P. nemoralis，and the volatile components were separated and determined by GC-MS. Human hepatic cancer Huh-7 cells were cultured with 0（blank control），5，10，20，30，40 and 50 μg（medicinal material）/ml extract for 24 h，and then MTT assay was used to detect the inhibitory effect of the extracts on cells. Relative cell viability and IC50 were calculated. The anti- bacterial activities of extract to Staphylococcus aureus，Methicillin-resistant Staphylococcus aureus，Enterococcus faecalis and other strain were determined by Kirby-bauer method and broth dilution method. RESULTS：Forty compounds were identified from the SFE-CO2 extracts from the roots of P. nemoralis. The main constituents were（Z，Z，Z）-9，12，15-octa-decatrien-1-ol，glycerin，cinnamaldehyde， n-hexadecanoic acid and eugenol. Compared with blank control group，SFE-CO2 extracts from the roots of P. nemoralis 5 μg（medicinal material）/ml and above showed significant inhibitory effect on cell growth（P＜0.05），and the inhibitory effect was strengthened as the concentration of extracts increased，IC50 values was 5.2 μg（medicinal material）/ml. However，the supercritical extract didn’t showed antibacterial activity against three microorganisms in 2 kinds of antibacterial tests. CONCLUSIONS： SFE-CO2 and GC-MS method can effectively extract and identify volatile components of the roots of P. nemoralis，and supercritical extracts can inhibit the viability of cells but have no antibacterial activity.