Base on the theory that tightly coupling can extend the bandwidth of the antenna, the rule in variations of antenna impedance in the strong coupled environment was used to study the influence of patch and metal ground on the impedance of the designed antenna. A new tightly coupled ultra-wideband internal conformal shape antenna which could be embedded in the metal box was introduced. The simulation results showed that the S11 of the designed antenna was less than -10 dB in the broad band from 0.8 GHz to 3.2 GHz, while the gain was greater than 3 dBi. Obviously, the designed antenna could meet the performance requirements of the train radio communication system for the wideband and conformal shape performance.