Abstract: TA2 titanium alloy plate with 16 mm thickness was tested by hybrid welding process of plasma arc welding for back welding and tungsten inert gas arc welding for cover welding(P-T hybrid welding).Single-sided welding and double-sided forming without beveling was achieved by keyhole plasma arc welding.The results showed that microstructure of weld consisted of a small amount of serrated α-Ti and acicular martensite, no component segregation and aggregation, inclusions, cracks and other defects were found.Microstructure of heat affected zone and fusion line were serrated α-Ti and lath martensite.Tensile strength of welded joints reached 486 MPa, which was equivalent to base materials, and fracture position was located in the heat affected zone.Being welded under preferable welding parameters, microhardness of weld and heat affected zone was 175 HV0.1 and 170 HV0.1, respectively, which were higher than that of base material.Therefore, P-T hybrid welding was capable of welding thick plates of titanium alloys and showed extensive application prospects in welding of thick titanium alloys.Highlights: For the first time, defect-free welding of 16 mm thick titanium was achieved by P-T hybrid welding