Fiber　laser-tungsten　inert　gas　(TIG)　hybrid　welding　is　applied　to　TC4　sheet　with　the　thickness　of　1　mm.　The　influences　of　welding　parameters　such　as　laser　power,　arc　current,　the　distance　of　heat　sources　and　the　shielding　gas　on　weld　bead　formation　are　studied.　The　metallographic　structure　and　mechanical　properties　are　also　analyzed.　The　results　indicates　that　with　the　increasing　of　arc　current　and　the　ratio　of　He　in　main　shielding　gas,　the　welding　fusion　area　gradually　increases.　With　the　increasing　of　laser　power　and　the　distance　of　heat　sources,　the　welding　fusion　area　changes　in　fluctuation.　The　tendency　of　undercut　is　related　to　the　heat　input　of　hybrid　heat　sources.　With　the　rising　of　concentration　and　input　of　the　energy,　the　undercut　depth　on　the　back　side　of　the　welding　seam　decreases.　The　efficiency　of　shielding　is　mainly　determined　by　the　heat　input　of　arc.　The　more　input　heat　is,　the　poorer　protective　effect　is.　The　tensile　strength　of　hybrid　welding　joint　under　optimum　welding　conditions　is　larger　than　the　base　metal,　and　the　elongation　is　smaller　than　the　base　metal.　This　is　related　to　the　distribution　of　martensite　in　the　welding　seam.　The　fracture　takes　place　in　the　base　metal.