Using the Generic-software ANSYS, numerical simulation analyzing on the dynamics characteristic of a Half-through reinforced concrete arch bridge is done. Its self-vibration parameters such as self-vibration frequencies, modes and so on, are given, as well as its modes characteristics are summarized. Besides, influence of the main structure parameters to the self-vibration characteristic is analyzed by varying these parameters of the arch bridge. The results show that self-vibration frequencies increase with rise/span ratio decrease; transverse support will help to enhance the lateral rigidity, reduce its out arch-plane vibration, and improve the stability in wind; the frequency of each vibration mode is increased with a approximate linearity with improvement of arch stiffness. So we can change arch stiffness to adjust its vibration characteristics. The results can offer reference to the seismic design of the similar bridge .