Superplastic deformation mechanical behavior of laser welded joints of TC4 alloys was investigated by hot tensile tests. Non-uniform deformation coefficient K was introduced to characterize the non-uniform deformation between welded joints and base metal during superplastic deformation. Results show that the laser welded joints of TC4 alloys can bear high-temperature superplastic deformation without damage. When the initial strain rate was below 10-2 s-1, the flow stress was below 60 MPa. Both the deformation rate of joints and K value of specimens were first increased and then decreased with increase of the deformation temperature and strain rate. At 900 oC and 10-2 s-1, superplastic deformation rate of joints and K value reach their maximum of 46% and 0.18, respectively at the same time. It reveals that the welded joints have better superplastic deformability, and sensitive index of strain rate m is bigger than 1.5