Wire　and　arc-based　additive　manufacturing　(WAAM)　is　a　rapidly　developing　technology　which　employs　a　welding　arc　to　melt　metal　wire　for　additive　manufacturing　purposes.　During　WAAM　of　thin-walled　structures,　as　the　wall　height　increases,　the　heat　dissipation　to　the　substrate　is　slowed　down　gradually　and　so　is　the　solidification　of　the　molten　pool,　leading　to　variation　of　the　bead　geometry.　Though　gradually　reducing　the　heat　input　via　adjusting　the　process　parameters　can　alleviate　this　issue,　as　suggested　by　previous　studies,　it　relies　on　experience　to　a　large　extent　and　inevitably　sacrifices　the　deposition　rate　because　the　wire　feed　rate　is　directly　coupled　with　the　heat　input.　This　study　introduces　for　the　first　time　an　in-process　active　cooling　system　based　on　thermoelectric　cooling　technology　into　WAAM,　which　aims　to　eliminate　the　difference　in　heat　dissipation　between　upper　and　lower　layers.　The　case　study　shows　that,　with　the　aid　of　thermoelectric　cooling,　the　bead　width　error　is　reduced　by　56.8%,　the　total　fabrication　time　is　reduced　by　60.9%,　and　the　average　grain　size　is　refined　by　25%.　The　proposed　technique　provides　new　insight　into　bead　geometry　regulation　during　WAAM　with　various　benefits　in　terms　of　geometric　accuracy,　productivity,　and　microstructure.