This　study　investigated　innovative　advanced　oxidation　processes　(AOPs)　combining　far-UVC　radiation　at　222　nm　with　sodium　percarbonate　(SPC)　to　effectively　remove　methotrexate　(MTX).　UV222　significantly　enhanced　the　direct　photolysis　and　AOP　degradation　of　MTX.　•OH,　CO3•-,　and　direct　photolysis　were　primarily　involved　in　the　degradation,　with　their　relative　contribution　being　in　the　order　•OH　＞　CO3•-　＞　direct　photolysis.　The　fluence-normalized　steady-state　concentrations　of　both　CO3•-　and　•OH　in　UV222/SPC　were　7.76　and　4.05　times　higher,　respectively,　than　those　in　UV254/SPC.　Transformation　product　analysis　revealed　distinct　MTX　degradation　pathways　and　varied　degradation　rates　of　MTX　substructures　between　the　systems,　with　the　order　in　UV254/SPC　being　4-aminobenzamide　(ABZ)　＞　2,4-diamino-6-(hydroxymethyl)　pteridine　(DHP)　＞　l-glutamic　acid　(LG)　and　that　in　UV222/SPC　being　DHP　＞　ABZ　＞　LG,　suggesting　different　reactivities　of　MTX　moieties　under　each　system.　The　presence　of　HCO3-　and　HA　inhibited　the　MTX　degradation,　whereas　NO3-　promoted　it,　in　the　UV222/SPC　system.　In　addition,　UV222/SPC　demonstrated　a　lower　energy　consumption　compared　to　UV254/SPC,　highlighting　its　potential　for　cost-effective　wastewater　treatment　applications.　This　study　offers　new　insights　into　the　mechanisms　of　UV222/SPC　systems　and　provides　guidance　for　the　development　of　technologies　for　the　removal　of　emerging　contaminants.　©　2024　American　Chemical　Society.