Abstract: The direct navigation accuracy of ship model is an important factor which influences the test results. With the navigation test for the large bridge of intercity railway in Xiangtan as a case study, we analyzed the errors caused by inadequate direct navigation performance. It was found that electric motor system largely affected the direct navigation performance of ship model. Better synchronization performance of the motor system reduced the differences between two motors on parallel circuit and improved the direct navigation performance. By changing the motors of propulsion system and the materials and fixation of balances, together with improving the mode of transmission connection, the balance rudder angle decreased by 2°-3° compared with the original scheme. The direct navigation performance was improved, and the accuracy was guaranteed. The improvement measures could be referential for similar ship model tests. 

Key words: navigation test in bridge area, ship model, direct navigation performance, balance rudder angle, improvement measures