Abstract: After the peanut histone deacetylase AhHDA1 is overexpressed in peanut hairy roots, the proportion of hairy roots with shorter lateral roots increases. The gene expression test results showed that the overexpression of AhHDA1 up-regulated the expression levels of the cell cycle-related gene AhCYCD4 and the auxin signal transduction-related gene AhIAA28 while the expression level of AhARF19 was significantly inhibited. Further LUC experiments found that AhHDA1 activates the transcriptional activity of AhCYCD4 and AhIAA28 promoters. It indicates that AhHDA1 may affect the growth of peanut hairy roots with lateral roots by regulating auxin signaling and cell division.