The hot deformation behavior of uniform fine-grained GH4720 Li alloy was studied in the temperature range from 1040 to 1130℃and the strain-rate range from 0.005 to 0.5 s~(-1) using hot compression testing.Processing maps were constructed on the basis of compression data and a dynamic materials model.Considerable flow softening associated with superplasticity was observed at strain rates of 0.01 s~(-1) or lower.According to the processing map and observations of the microstructure,the uniform fine-grained microstructure remains intact at1100℃ or lower because of easily activated dynamic recrystallization(DRX),whereas obvious grain growth is observed at 1130℃.Metallurgical instabilities in the form of non-uniform microstructures under higher and lower Zener-Hollomon parameters are induced by local plastic flow and primary γ’ local faster dissolution,respectively.The optimum processing conditions at all of the investigated strains are proposed as 1090-1130℃ with 0.08-0.5 s~(-1) and 0.005-0.008 s~(-1) and 1040-1085℃ with 0.005-0.06 s~(-1). The hot deformation behavior of uniform fine-grained GH4720 Li alloy was studied in the temperature range from 1040 to 1130 ° C and the strain-rate range from 0.005 to 0.5 s ~ (-1) using hot compression testing. Processing of maps were constructed on the basis of compression data and a dynamic materials model. Canciderable flow softening associated with superplasticity was observed at strain rates of 0.01 s ~ (-1) or lower. According to the processing map and observations of the microstructure, the uniform fine-grained microstructure remains intact at 1100 ° C or lower because of easily activated dynamic recrystallization (DRX), an obvious grain growth was observed at 1130 ° C. Metallurgical instabilities in the form of non-uniform microstructures under higher and lower Zener-Hollomon parameters are induced by local plastic flow and primary γ ’local faster dissolution, respectively. The optimum processing conditions at all of the investigated strains are proposed as 1090-1130 ℃ with 0.08-0.5 s -1 nd 0.005-0.008 s ~ (-1) and 1040-1085 ℃ with 0.005-0.06 s ~ (-1).