Tensile testing was performed on fine-grained GH4169 superalloy sheet at elevated temperatures (920°C~980°C) and at different initial strain rates (10-4~10-2s-1). The maximum elongation obtained was 280%. By TEM, active dislocation movement was observed and compared at different strain level and strain rate. Dynamic recovery and recrystallization was also found during superplastic deformation that played an important role of softening. At last the superplastic deformation mechanism of GH4169 alloy was discussed.