Based on AMESim，a method of dynamic characteristics analysis and optimization for hydraulic system of a self-propelled steel bridge (SPSB) is presented. The approach of this work includes steps of (1) modeling the hydraulic system by defining components and their parameters according to working conditions; (2) evaluating control modes of the system, testing performance of components and analyzing main factors causing load-impacted and movement-unsynchronized of cylinders in the system by repeated changing and running of the model; and (3) improving the system. The results of this research show that sudden change of piston-rod movement and fluid pressure in hydraulic cylinders could lead to larger load-impacted of the system, and fluid pressure loss and load change of hydraulic cylinders would greatly effect on stability and synchronization of the system; but accumulators installed in the circuits can effectively decrease load impact and enhance movement steady of cylinders, and proportional valves used to control the circuits can obviously improve synchronization performance of cylinders.