Abstract: Laser lap welding process of ultra-thin industrial pure titanium alloy was explored in the paper. Laser welding process test was carried out on 0.1 mm thick ultra-thin TA1 sheet. The causes and restraining measures of weld formation defect and inner porosity defect were analyzed. The relationship between process parameters and weld formation was studied from defocusing distance and heat input. Finally,the mechanical properties of the weld were tested by tensile test. The experiment results showed that defects such as burn-through could be avoided by reasonably selecting welding parameters,and the porosity defect mainly distributed at both ends of the fusion surface. With the increase of laser heat input and the decrease of defocusing distance,the weld shape changed from circular-arc shape to V shape and then to X shape,and the width of fusion surface increased gradually. After laser welding,TA1 could meet the minimum tensile strength requirement of the fuel cell bipolar plate to the base metal,which provided the basis for the application of TA1 titanium alloy in the fuel cell industry.