Abstract: For rapid recovery shock isolator design, a novel expression has been addressed to turn time from index function to restraint variable. Equations of displacement and acceleration peak are derived through shock response characteristic of SDOF system with different constraints. Then the design problem is modeled into ten programming functions whose constraints and index are both nonlinear. They are calculated by means of SQP method, and results provide insight into some important characteristics and design principles of rapid recovery shock isolator. In the end a graphical design method is put forward for application. The results represent a preliminary step in the development of theory of rapid recovery shock isolation, and are valuable in application.