Customer requirements are constantly evolving, which will cause high change risks and redesign costs for the products. To control the change risks toward evolving customer requirements, margins are widely used in recent studies. Margins are the redundant values of design parameters, and they can absorb potential change risks of customer requirements. Nevertheless, the existing research does not well explore the relationship between margins of design parameters (MDPs) and change risks, i.e., how much each MDP should be predetermined for absorbing the potential change risks is unknown. Thus, to manage the evolving customer requirements, in this article, an optimization method considering the MDPs and change risks is proposed. First, the functional basis model of the product is established to obtain the relationships between design parameters. Second, change risks are analyzed based on the relationships between design parameters and the improved change prediction method. Third, the benefits and costs of MDPs in reducing change risk are analyzed, based on which, an optimization model for MDPs is established and solved. Finally, the optimization of MDPs for the hair dryer is implemented as a case study to illustrate the utility and effectiveness of the proposed method.