This paper presents an automatic optimization method for compliant constant force mechanisms, which eliminates the need for time-consuming parameter tuning and complex model design in the conventional design process. The proposed optimization framework is based on the finite-element analysis (FEA) and multi-objective genetic algorithm (MOGA) methods and is designed in two steps: First, the preliminary mechanism design is carried out to roughly encompass the specified constant force objective; then, the preliminary model is optimized by applying a MOGA based on FEA results. The optimized model can achieve the desired performance automatically while achieving a larger constant force stroke, which is verified by performing FEA simulations and experimental studies. The experimental results demonstrate that the designed CFMs increase the constant force stroke by 16.3% while achieving the specified design accuracy compared to the preliminary prototype.