Abstract: To investigate the role of WRKY transcription factors（TFs） in sensing saline-alkali stress signals and maintaining their tolerance function through physiological and biochemical regulatory pathways, and the WRKY42 gene of Amorpha fruticosa was cloned and the expression pattern in response to salt（NaCl） and alkali（NaHCO3） stress and tissue organs was analyzed, and the salinity tolerance function was also studied its by overexpression in tobacco. In this study, the AfWRKY42 gene was cloned based on transcriptome sequencing data of A. fruticosa L. under stress. Bioinformatics analysis showed that AfWRKY42 contained a WRKY structural domain, two low-complexity regions and a helix region. Phylogenetic tree analysis of amino acids revealed that AfWRKY42 was most closely related to WRKY47 of Cajanus cajan and WRKY42 of Mucuna pruriens. The localization of AfWRKY42 protein in mesophyll protoplasts of Arabidopsis thaliana was confirmed in nucleus by a transient gene expression system. Quantitative analysis of AfWRKY42 gene showed the highest expression in the shoot epidermis of Sophora japonica. Detection of expression patterns in roots and leaves treated with NaCl and NaHCO3 showed an overall increasing trend induced by it, suggesting that overall stress induced an increase in AfWRKY42 gene expression, and AfWRKY42 gene was associated with the regulation of salinity tolerance in plants. Analysis of salinity tolerance in 35S-initiated overexpressing T3 generation of tobacco lines transgenic for AfWRKY42 gene showed that the transgenic tobacco lines showed increased resistance after salinity stress treatment, it had higher chlorophyll and electrical conductivity and significantly lower malondialdehyde content than the wild type, indicating that AfWRKY42 played an important regulatory role in response to salinity stress. It would provide a WRKY transcription factor candidate gene for salinity resistance breeding and lay the foundation for improving the resistance of A. fruticosa and other plants.