To understand the production pattern of H2S and its potential function in mastitis, endogenous H2S production in supernatant was monitored by a Micro H2S Content Assay Kit, and the expression of key enzymes in H2S synthesis, including CTH and CBS, were evaluated by Immunofluorescence (IF), qRT-PCR and WB assays, respectively, in LPS-induced MAC-T cells. The gene discussed is CTH; the disease is mastitis.