Abstract: The U-box domain genes typically exist in multiple variants within plant genomes, and most of them belong to the ubiquitin/proteasome system as E₃ ubiquitin ligase. They play key roles in the regulation of growth, in development, in reproduction as well as in response to environmental stress. In this study, bioinformatics methods were applied to identify U-box family genes of M. truncatula through whole genome screening. A phylogenetic tree was created using the MEGA6 program. Gene structure and chromosome location were defined by GSDS and Mapinspect. A total of 41 U-box genes distributed unevenly on 8 chromosomes were identified from M. truncatula. The U-box proteins were classified into six major classes based on their motif compositions and phylogeny relationships. The expression profiles of M. truncatula U-box genes showed characteristics of tissue specificity and response to salt, drought and nitrogen stress. These results will be useful for future functional analyses of the U-box family genes in M. truncatula.