Abstract:[Background] Armillaria are medicinal and edible fungi having a parasitic or saprophytic phase, and it is vital to study the differentially expressed genes in these fungi. However, there are few reports on the internal reference genes of them. [Objective] To screen out the optimal internal reference genes for Armillaria mellea 541 under different experimental conditions. [Methods] In this study, ACT-1, α-TUB, β-TUB 1, γ-TUB, UBQ, EF-1γ, 18S rRNA BP, and GAPDH were used as candidate reference genes of A. mellea 541. The A. mellea 541 hypha (AH) and rhizomorph (AR) cultured on potato dextrose agar (PDA) medium were used as the control group, and those cultured on the PDA medium supplemented with diphenyleneiodonium chloride and sawdust as inhibitor group and inducer group, respectively. The expression levels of the eight genes were evaluated by RT-qPCR and BestKeeper. [Results] EF-1γ was selected as the optimal reference gene for A. mellea 541 because of its stable expression under different experimental conditions. [Conclusion] This study provides a reliable reference gene for analyzing the gene expression in Armillaria spp..