Abstract: To explore the relationship between the Catalase（CAT） gene and saline-alkali stress tolerance of Lilium pumilum, the CAT gene was successfully cloned from L. pumilum bulb. The length of region ORF was 1 479 bp, encoding 492 amino acids, and sequence alignment and phylogenetic tree analysis were performed, and the Catalase protein of L. pumilum was found to be closely related to the Catalase proteins of L. sargentiae, Ananas comosus, Elaeis guineensis and other plants. The Catalase protein was induced to express, and purified in vitro with 1 mol·L^-1 IPTG as the inducer after constructing prokaryotic expression vector pQE-LpCat. The results showed that the growth concentration of bacteria solution containing PQE-LpCat protein was higher than that of the control strain under the stress of 50 mmol·L^-1 NaHCO₃. Under the stress of 1 mol·L^-1 NaHCO₃ and 2.5 mol·L^-1 H₂O₂, less wilting was observed in plants overexpressing the LpCAT gene compared to wild-type. Determination of the physiological indexes including net photosynthetic rate, stomatal conductance, intercellular CO₂ and transpiration rate, H₂O₂ concentration and contents of malondialdehyde（MDA） showed that tobacco plants overexpressing the LpCat gene were more tolerant to saline and alkali stress than wild-type tobacco plants.