Abstract: Hydrogenation can improve the uniformity of superplastic deformation of TC4 titanium alloy laser weld. The non-uniform deformation coefficient K was introduced to quantitatively characterize the non-uniform deformation. The results indicate that when the hydrogen content exceeded 0.2%, the super plastic property of welded joint degraded with the increase of hydrogen, with increase of peak flow stress and decrease of percentage reduction in area, but the uniformity of superplastic deformation increased. With the increasing of hydrogen content, the percentage reduction in area of base metal decreased more than that of welded joint. The non-uniform deformation coefficient K can characterize the non-uniform deformation of the titanium alloy laser weld and base materials with hydrogenation during superplastic deformation. The K value increased with the increase of hydrogen content, the increase of temperature, and the decrease of strain rate. The K value reached the maximum value 0.84 when the hydrogen content was 1.299%, the deformation temperature was 920℃, and the strain rate was 10^-4s^-1.