MwMYB4 gene is a member of the MYB transcription factor family cloned from Agropyron mongolicum Keng. The progeny of transgenic Arabidopsis with MwMYB4 gene were used as materials in this study. The phenotype analysis and molecular identification of transgenic plants under drought and low temperature stress were used to analyze and verify the function of MwMYB4 gene. The results showed that： (1) the MwMYB4 gene has been successfully integrated into the genome of transgenic T₁ A. thaliana and achieved transcriptionlevel expression. (2) Under drought stress， the transgenic A. thaliana plants showed less yellowing， and the relative conductivity was lower than that of the wild type， but the change was not significant. The content of proline was significantly higher than that of the wild type control. The expression level increased with the duration of drought stress. (3) Under low temperature stress， the paleness of transgenic Arabidopsis leaves was significantly lower than that of wild type， and the expression level of MwMYB4 gene increased with the increase of low temperature stress time. Studies have shown that overexpression of MwMYB4 gene from Agropyron mongolicum can increase the tolerance of transgenic Arabidopsis to drought and low temperature. This gene may play a regulatory role in the regulation mechanism of drought stress and low temperature stress, and can be an important candidate gene for improving drought and cold resistance of crops and other forages.