Abstract: The effects of track stiffness on track dynamic characteristicswere investigated by the wheel-rail system dynamic analysis in frequency domain. The concepts of sensitivity coefficients of track dynamic parameters to track stiffness were put forward and defined. The method of dynamic optimization was proposed for the global track stiffness and the ratioof fasteningstiffness to ballaststiffness on the basis ofthe characteristics of the sensitivity coefficients. As an example, this method was applied to research track stiffness in a high-speed railway in China. The result shows that the optimum global track stiffness ranges from 62 to 86.9 kN/mm and the optimum ratio of fastening stiffness to ballast stiffness is about 0.5.