Steering gear is an important device on a ship,whose performance quality affects ship greatly.Aiming at high power-density steering gear which is composed of electro-hydraulic system and ball rotary-oscillating actuator,a mathematics model of the steering gear system is deduced.The system optimization design is carried out using optimization theory.Dynamic simulations of the pre and post optimized systems are made by MATLAB software to analyze dynamic characteristics.The analysis results show that the optimized steering gear can meet practical needs.