Abstract: The simulation of the iodine well was studied by the neutron multiplication theory. Firstly, the model of simulation for the iodine well was established. Then, the reactivity worth of xenon poisoning in different initial neutron densities was studied by this model, and the result was compared with result of the point reactor model. The result shows that the relationship between the depth of iodine well and the initial neutron density was linearity. In the end, the maneuverability of the reactor in iodine well was studied by this model. The conclusions are very important to the safety analysis and operation of ship nuclear reactors.