Sulfur-siderite driven autotrophic denitrification (SSAD) has received increasing attention for nutrient removal in constructed wetlands (CWs). Nevertheless, its effectiveness in simultaneous water purification and greenhouse gases (GHGs) reduction remains obscure. In this study, three vertical flow constructed wetlands (VFCWs), filled with quartz sand (CCW), sulfur (S-CW), and sulfur-siderite mixed substrates (SS-CW), were constructed to investigate the underlying mechanisms of SSAD on water purification enhancement and GHGs reduction. Results indicated that SSAD optimized the carbon, nitrogen, phosphorus, and sulfur transformation processes and enhanced the electron transfer system activity (ETSA) in CWs. Meanwhile, it resulted in the highest total nitrogen (TN) removal efficiency (91.6 ± 2.2 %) and the lowest methane (CH