Abstract: The dynamic mechanical properties of dual-phase high strength steels HC340/590DP and HC700/980DP for vehicles were studied by room temperature tensile tests at different strain rates (0.001-500 s^-1). The flow stress-strain curves of the two steels were fitted by Johnson-Cook model, Swift Hockett/Sherby model and the modified model obtained by introducing Swift Hockett/Sherby model into Ludwik model, and the fitting results of the three constitutive models were compared and analyzed. The results show that with increasing strain rate, two steels both exhibited the phenomenon of strengthening and plasticizing. The average fit values of Johnson-Cook model, Swift Hockett/Sherby model, and modified Ludwik model were 0.950, 0.999, 0.997, respectively. The modified Ludwik model not only had the coupling characteristics of stress at each strain rate, but also maintained the high fitting accuracy; it could accurately describe the dynamic rheological behaviors of dual-phase high strength steels for vehicles.