Hepatoprotective and antioxidant activities of Acer mono and A. okamotoanum were compared after beingextracted by low temperature and high pressure (LTHP) at 20 MPa and 60℃ for 15 minutes. Extraction yield of both A.mono and A. okamotoanum was increased about 40~43% by this extraction process. On scavenging activities, the bark of A.okamotoanum from this extraction process showed the highest activity as about 97%. This value was higher than that fromconventional water extraction and A. mono extracts. Both of A. mono and A. okamotoanum showed high ability on nitritescavenging, but decreasing tendency according to increasing of pH. On SOD-like test, A. okamotoanum had the highestactivity as 46.28% at 1.0㎎/㎖ concentration. A. okamotoanum extracted by LTHP also showed the highest activity as197.38% in adding 1.0㎎/㎖ concentration. Generally, the extracts from low temperature and high pressure extraction pro-cess are higher hepatoprotective and antioxidant activities than that from conventional water extraction. It can concludethat the bark of A. okamotoanum has better biological activities than other parts of A. mo