In order to study the mechanical behavior of Ti6321 alloy under high temperature and high strain rate,the dynamic compression behavior of Ti6321 alloy at room temperature( 25 ℃) and high temperature( 200,400,600 ℃)was investigated using a Split Hopkinson Pressure Bar. The mechanical properties,strain rate sensitivity and temperature sensitivity under high temperature and high strain rate were studied. A clustering global optimization algorithm was used to construct the Johnson-Cook constitutive model of Ti6321 alloy with bimodal microstructure under the strain rate of 103 s-1. The results demonstrate that Ti6321 alloy has a strain rate hardening effect both at room temperature and high temperature,but the effect of strain rate on flow stress is not as obvious as that of test temperature. As the test temperature increases,the flow stress decreases significantly,and the temperature sensitivity factor increases. The curve fitted by the Johnson-Cook constitutive model is in good agreement with the experimental curve,and the model can be used for mechanical simulation of Ti6321 alloy at high strain rates.