Objective: The characterization on growth and some secondary metabolites of Artemisia annua hairy roots were investigated. Method: We investigated the effects of plant growth regulators such as NAA and GA3 on the hairy roots and untransformed roots. The main components of some secondary metabolites were tested in the hairy roots. Result: NAA at lower concentration (0.01-0.05 mg ·L-1) could promote formation of lateral and branch roots and had no effect on untransformed roots. High concentrated NAA (0.1 mg ·L-1) inhibited the growth of hairy roots but stimulated the growth of untransformed roots. Artemisinin was not detected in untransformed roots

but at 0.64 mg ·g-1 in hairy roots. To the flavonoids in A. annua

chrysoplenetin was found in both roots

but there was a higher content of arteannuin (0.76 mg ·g-1) in hairy roots

3.5 folds of that in untransformed roots. Conclusion: A. annua hairy roots have a unique characterization on growth and secondary metabolites.