The work aims to improve the accuracy and efficiency of dynamic modifications for large complex structures. With the high-power engine cylinder head as an object, first of all, on the basis of the measured natural frequency and by comparing the natural frequency and the measured frequency calculated in finite element method, the frequency with bigger error was found out, and then the sensitive parameters of the frequency were discovered through the sensitivity analysis. Finally, the parameters were optimally designed and modified in design parameter modification method. The calculated value of natural frequency of the cylinder head subject to dynamic modification was closer to the test value and could satisfy the using requirements of the project. The modified finite element model combined with design parameter method and sensitivity analysis method can more accurately reflect the dynamic characteristics of the structure, which can improve the efficiency of the structural dynamic modification.