Based on Fluent 6, numerical simulation code for solving aeroelastic problems is first presented by using loosely coupled method in this paper. The fluid domain can be solved by adopting serial or parallel computation method, and the structure domain is solved by adopting Newmark method, and finally the interface coupling between the fluid and structure domains is implemented through dynamic mesh technique. The calculation process and the special method to deal with the parallel computation in fluid domain are then introduced. Finally, numerical simulation of vortexexcited vibration of a 2D square cylinder at Reynolds number of 22000 is done. The computed results and the comparison with those in literatures could verify the validity of the present program.