This paper presents big bang-big crunch (BB-BC) method for the optimization of preventive control action to enhance the dynamic security of the power system against transient instabilities. In the proposed approach, generation rescheduling is selected as a preventive control action and this control action is considered as a constrained optimization problems where the constraints are dynamic security of the system, generation limits and loading capabilities of transmission lines. The security constrained generation rescheduling is implemented through BB-BC method which optimizes the total fuel cost during the preventive control. The proposed method is applied to 50 generator 145 bus IEEE test system and the effectiveness of the approach is discussed. © 2012 IEEE.