Abstract: The influences of temperature and strain rate on the flow behavior, dynamic softening mechanism of H18 2024 aluminum alloy during plastic deformation process at elevated temperatures were investigated, according to the stress-strain curves at temperatures of 300-475 ℃ and strain rates of 0.000 5-0.1 s-1from tensile testing and microstructure observation. Results show that recrystallization took place in plastic deformation of H18 2024 aluminum alloy at elevated temperatures above 300 ℃, and equiaxed grains were obtained after deformation at 475 ℃ with strain rate of 0.000 5 s-1. The tensile elongation of H18 2024 aluminum alloy rose first and then dropped with the increase of temperature and strain rate. The maximum stress and strain hardening index of the aluminum alloy reduced with the increase of temperature or the decline of strain rate, and the strain rate sensitivity index increased when temperature was elevated.