Object To study the effect of rare-earth elements La3+ on growth of hairy roots and normal roots of Rheum palmatum L and their yield of anthraquinones. Methods The biomass and an- thraquinone yield of two hairy clones DH5c, DH7a, and normal root NOR cultures of R. palmatum were evaluated statistically after various concentration of La3+ were administrated into culture medium. Results Significant differences of biomass yield and anthraquinone yield were shown among six La3+ concentrations, in which 10 mg/L showed obvious inhibitory effect for root growth and 1. 0 mg/L was the best for anthraquinone yield. In general, aloe-emodin and rhein were predominant in five anthraquinones after treated with the rare-earth element. Conclusion The growth of hairy root cultures of R. palmatum and their anthraquinone yield are greatly promoted by addition of La3+ to the medium.