The temporal spectral element method is adopted to solve the dynamic differential equations. An in depth exploration of discrete dynamic response in time domain is considered to transform a system of second order differential equations into first order differential equations by using Bubnov-Galerkin method. The dynamic responses are accurately and efficiently calculated. The critical points and adjacent GLL points method is proposed，in addition, it is proposed that spectral element division and number of times of interpolation are functions of variability of dynamic loads. Two optimization examples of spring shock absorber and the five DOFs vehicle suspension system are given. The artificial design variable is introduced. A detailed analysis of the advantages and disadvantages for proposed method to deal with time-constraints is done, but shows the correctness of this method. These can provide a reference to be further optimized dynamic response.