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.　center　dot　OH,　CO3　center　dot-,　and　direct　photolysis　were　primarily　involved　in　the　degradation,　with　their　relative　contribution　being　in　the　order　center　dot　OH　＞　CO3　center　dot-　＞　direct　photolysis.　The　fluence-normalized　steady-state　concentrations　of　both　CO3　center　dot-　and　center　dot　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.