Abstract: The button mushroom（Agaricus bisporus） is prone to epidermal browning during postharvest storage, and the underlying molecular mechanism has not been clarified entirely. In order to explore the molecular mechanisms involved in the postharvest browning of A. bisporus, the genome-wide AbHMG transcription factors have been identified,and the characteristics of the AbHMGs and the expression patterns of the AbHMG genes during postharvest storage have been detected. The results showed that 13 AbHMG transcription factors were identified based on the PFAM annotation, with a coding sequence length of 425～1 881 bp, and encoding 141～626 amino acids. The relative molecular weight and isoelectric points of AbHMGs were 15 996～69 651 and 5.12～11.13. The major structural elements of AbHMGs were α-helix and irregular curl and all the AbHMGs were found to be unstable proteins located in the nucleus.The L*values of the button mushrooms’ surface gradually decreased during storage, indicating an increase in browning. Additionally, the relative conductivity and respiration intensity of the button mushrooms’ bodies increased gradually. Fluorescent quantitative PCR analysis showed that, the expression level of AbHMG7, AbHMG9, and AbHMG13was upregulated during the late stage of storage. In conclusion, 13 HMG transcription factors were identified in button mushrooms, and the AbHMG7, AbHMG9, and AbHMG13 transcription factors may be involved in the transcriptional regulation processes related to the browning of button mushrooms after harvest.