Abstract: This research aims to explore the physiological and biochemical characteristics changes and differences of Lagerstroemia speciosa and Lagerstroemia balansae under drought stress. With annual seedlings of L.speciosa and L.balansae as test materials, the experimentation was designed in random block design, set 4 treatments ie. treatment with L.speciosa normal water supply, drought, L.balansae normal water supply, drought, and mainly determined biomass, protective enzyme activity, osmotic adjustment substance content and other physiological indicators of Lagerstroemia indica seedlings. The results showed that under drought stress, the biomass, leaf water content and chlorophyll content of L.speciosa did not change significantly. However, the biomass of L.balansae decreased significantly by 21.98%, and the leaf water content and chlorophyll content also decreased remarkably. The relative electrical conductivity, malondialdehyde (MDA) content, peroxidase (POD) activity, catalase (CAT) and superoxide dismutase (SOD) activity of L.speciosa and L.balansae were significantly increased. This research proves L.speciosa and L.balansae have a certain ability to resist drought, but drought resistance ability of L.speciosa is better than the L.balansae.