The superplasticity of fine grained Ti-6Al-4V wide sheet was investigated by constant strain rate tensile method in this work. The superplastic tensile tests were carried out at temperatures ranging from 1103K to 1223K and strain rates from 3.2×10-4 s-1 to 1×10-2s-1. The tensile elongation to failure values between 100% and 604% were obtained. Microstructure evolution and deformation mechanism were analyzed. The main deformation mechanism was grain boundary sliding, accommodated by matrix dislocation movement and the intragranular slip of β phase. It was also found that the Ti-6Al-4V wide sheet showed anisotropy when deformed at lower temperatures, which was obviously reduced when deformed at higher temperatures.