The invention provides a design method for a connecting rod. The connecting rod includes a first end, a shank and a second end; and the shank is connected between the first end and the second end. The design method includes: determining a weight m1 of a standard steel connecting rod; determining a weight m2 of a nodular cast iron connecting rod having the same size with the standard steel connecting rod; and simulating to reinforce the shank with a reinforcement material having a preset weight m, and calculating a size of the reinforced shank; where m1>m2, and m