Abstract: Studies on production of plant secondary metabolites by hairy roots have been increasing over the last 30 years. But there are constraints for commercialization of hairy root culture，because there is a lack of detailed knowledge about the mechansm affecting biosynthetic pathways in hairy roots. New insights in the effects on secondary metabolites biosynthesis by hairy roots are discussed，which comprise physical and chemical parameters，regulation technologies enhancing productivity，and key factors in bioreactors. The study on suitable bioreactor and methods enhancing mass transfer efficiency will make it possible to produce plant secondary metabolites by hairy roots at commercial level based on their morphological and physiological characteristics.