Abstract: Structure and principle of two kinds of steering systems for static load sensing and dynamic load sensing were analyzed and comapared.Result showed that dynamic signal priority valve had more advantages than static signal priority valve and could not be replaced.Dynamic signal priority valve had been widely used in large power tractor steering system in foreign countries.It had also begun to enter the application in domestic large power tractor steering system.And it would be more and more widely used with the progress of science and technology.