Abstract: Modal tests are carried out in the development stage of a large solar array to find out its dynamic characteristics to improve the design and the finite element model. In this paper, the floating method and the suspension method are used, respectively, to simulate the free boundary. Modal tests are carried out by using the preload releasing method, the excitation methods with MB exciter and APS exciter, and the test results are compared and analyzed. It is shown that the swaying frequency measured by the suspension method is more accurate than that obtained by the floating method.