Abstract: Quadratic regressive factorial experiment and SPSS software was used to analyse and optimize concentrations of IBA and NAA added in rooting medium for the rooting rate，root length，root number，sprouting number，bud length，leaf number and shoot fresh weight of Catalpa bungei, we obtained a serial of regression equations. Using such equations to search for the best dosage of IBA and NAA to induce root in vitro culture of C. bungei. The results showed that, a certain concentration of NAA could promote the root differentiation and growth, and increase leaves, but there is no significant role to the growth of buds and sprouting number.The best dosage range of IBA is in 0.200—0.344 mg/L, and dosage range of NAA is in 0.023—0.073 mg/L, the rooting rate was achieved at 95 %, the probability of the event was 95 %.