A method for designing a flexible copper busbar of a power battery, the flexible copper busbar comprising a first connection portion, a second connection portion, and a convex portion connected between the first connection portion and the second connection portion; wherein the first connection portion comprises a first connection hole, and the first connection portion is connected with the first battery module via the first connection hole; and wherein the second connection portion comprises a second connection hole, and the second connection portion is connected with the second battery module via the second connection hole, the first battery module and the second battery module being adjacent to each other; the method being characterized in comprising: performing mode analysis to a previously established finite element grid model of the power battery to find a direction with a minimum rigidity in the finite element grid model of the power battery, the finite element grid model of the power battery being a finite element model in which real structures of a battery pack casing, battery modules, a high voltage box and a BMS are reflected, and both the mass of the flexible copper busbar and the mass of a harness of the power battery being added into the battery module; obtaining a signal of an extreme mechanical shock working condition, the signal of the extreme mechanical shock working condition corresponding to data presented when a maximum space is created between the first battery module and the second battery module; applying the signal of the extreme mechanical shock working condition in the direction with the minimum rigidity in the finite element grid model of the power battery to perform mechanical shock analysis in which the maximum space between the first battery module and the second battery module is obtained; and obtaining the total length of the flexible copper busbar by, first, subtracting an initial space between the first battery module and the second battery module from the maximum space, then, multiplying the result thus obtained by a predetermined safety factor, and then, adding an initial space between opposite ends of the flexible copper busbar to the result that has been multiplied with the safety factor, the value of the safety factor being selected from a range of 1 to 3. performing mode analysis to a previously established finite element grid model of the power battery to find a direction with a minimum rigidity in the finite element grid model of the power battery, the finite element grid model of the power battery being a finite element model in which real structures of a battery pack casing, battery modules, a high voltage box and a BMS are reflected, and both the mass of the flexible copper busbar and the mass of a harness of the power battery being added into the battery module; obtaining a signal of an extreme mechanical shock working condition, the signal of the extreme mechanical shock working condition corresponding to data presented when a maximum space is created between the first battery module and the second battery module; applying the signal of the extreme mechanical shock working condition in the direction with the minimum rigidity in the finite element grid model of the power battery to perform mechanical shock analysis in which the maximum space between the first battery module and the second battery module is obtained; and obtaining the total length of the flexible copper busbar by, first, subtracting an initial space between the first battery module and the second battery module from the maximum space, then, multiplying the result thus obtained by a predetermined safety factor, and then, adding an initial space between opposite ends of the flexible copper busbar to the result that has been multiplied with the safety factor, the value of the safety factor being selected from a range of 1 to 3.