The compressed shapes of the pellet driven by a radiation field in a cylindrical gold hohlraum under single ring driving of incident laser beams simulated by RT3D and Lared-Ⅰ codes are given. As the position of the incident laser spots changing, the temperature distribution on the pellet surface changes as well and the pellet shapes turned out to be cake-like, sausage-like or ball-like respectively according to the different position of the laser spots. The comparison of the simulation result with the experiment carried out in LLNL and with the simulation result by Lasnex codes is given here too and it is shown that the same conclusion and the similar numerical result was obtained. Meanwhile it can also be seen that under single ring driving, it is not enough to supply a uniform and symmetrical radiation fields and it would be necessary to develop two or three laser rings driving to improve the radiation field.