Abstract: The dynamic mechanical properties of LY12 aluminum were studied experimentally by Hopkinson Bar of diameter 5mm with an automatic assembling system and heating system,within the range of temperature from 20℃ to 400℃ and strain-rate from 5×10³s^-1 to 1.4×10⁴s^-1.In the experiments,a shaper was used to eliminate the oscillation of high frequency in the incident signal and to improve the experimental precision of bar system.The experimental results show that the effect of temperature on dynamic properties of LY12 is not great at temperature lower than 200℃;on the contrary,the thermal softening effect is obvious at temperature higher than 200℃,exhibiting the decrease of flow stresses and linear harden modulus with increase of temperature,which is similar to linear harden materials.From the experiments,the dynamic properties of LY12 don't show strong sensitivity to the strain rates.