In this paper, the beam temperature and energy broadening of a charged-particle beam in an axially symmetric electric-field (including the average field causel by the space charge) are presented. The result shows that in the drift region, this kind of energy broadening is directly proportional to the beam current and inversely proportional to the macro flow velocitp of the beam, so that for a heavy-ion beam with higher current, it will become an important part in the total energy broadening. As a numerical estimation, the energy broadening of a 1H ion beam with energy 20keV and current 20mA in the drift region is 26.5eV, while under the same conditions, the 121Sb ion beam has an energy broadening of 291.5eV which increases linearly with the increasing of beam current. The result about the beam temperature shows that in the drift region, the effect of space charge of the beam raises the beam temperature.