The forming history should be taken into consideration to get more precise numeric simulation results in car crash simulations. In this paper the A6111T4P aluminum alloy sheet metal underwent different prestraining and baking treatment.  Then tensile tests were conducted to obtain flow stress curves. The HS flow stress model was selected and key factors influencing the fitting parameters in the HS model were analyzed using the method of inductive statistics based on experimental results. Finally, a novel flow stress model for aluminum alloy related to prestrain and baking was built.