In order to obtain modes and damping characteristics of beam-like carbon fiber composite truss, a solid finite element model is established for truss modes simulation. It is then proposed to compute the structural damping loss factors based on the simulated results, using modal strain energy damping model. To improve the effciency of modes analyzation, also, an equivalent analysis approach for truss modes is presented, which is based on beam equivalence theory. Comparisons are made among the simulated results, equivalent analysis results and actual measurement, respectively, which show that vibration shapes from equivalent analysis, simulation and the experiment agree well. In addition, errors of the simulated natural frequencies and the calculated structural damping loss factors are both less than 10%. These validate the applicability of both the presented modes simulation method and damping computation method. Finally, the equivalent analysis approach is demonstrated to be rather efficient for modes of large scale truss, based on the simulation results.