Aluminum alloys have been widely used in the ship industry for their low density, high specific strength and specific stiffness. However, compared with steel, the strength of aluminum alloy is low. To improve its strength, JDA1b aluminum alloy, which is often used in die casting and outfitting parts of ships, was taken as the research object. Pre-strain tensile, pre-bend tests and dynamic tensile tests were carried out to investigate the effects of pre-strain and pre-bend on the mechanical performance of JDA1b alloy, and the effects of strain rate on the flow behaviors of the alloy were also investigated. The results show that increasing the strain rate can increase the flow stress and tensile strength of the material; the yield stress and tensile strength of this material increase with the increase of pre-strain, and the elongation decreases, and that the increase of pre-bend is favorable to improve the bending yield load, bending stiffness and damage displacement of the material. A new dynamic constitutive model considering ultimate stress and critical strain was proposed, which allows the flow stress to be predicted more precisely at various strain rates over a wide range of 1~800/s, and the fitting goodness-of-fit value reached 0.999. This study provides methods to improve the strength of aluminum alloys, and the proposed constitutive model is conducive to the improvement of the accuracy of the simulation of mechanical performance of parts.