The commercial hot-rolled bars of LD10 alloy (grain size 25 similar to 75 mu m) are pretreated via proper recrystallization annealing (temperature 380 degrees C, 420 degrees C and 460 degrees C) and solution annealing (temperature 500 degrees C). The average elongation is increased from 158% to 270%, 223%, 219% and 233% respectively and the maximum elongation is 321% (500 degrees C, 3.3x10(-4)s(-1)). The test results show that the alloy can present certain superplasticity owing to structural effect of dynamic recrystallization refining during superplastic deformation of coarse-grained LD10 alloy. Large and deep cavities form in grain boundaries and result in intergranular fracture after larger superplastic tensile deformation. And a large amount of metal filaments appear on grain surfaces. The formation of filaments is attributed to viscous flow of solid-liquid mixture in grain boundaries caused by grain-boundary sliding. The appearance of solid-liquid mixture makes grain-boundary sliding easier.